It might be impossible to talk about this movie without spoiling the big twist.  It perhaps has already been spoiled by the fact that it is being analyzed by the time travel movies Examiner--and arguments that we have analyzed such films as Next, Minority Report, Terminator Salvation, and Peggy Sue Got Married, which arguably are not or might not be time travel movies are moot here.  So the spoiler is this:  despite the protestations of the characters operating the device, it turns out that they have actually built a type of time travel machine.  They do not realize it, because--well, that would be spoiling too much.

Most of what we know in the film we learn as Captain Colter Stevens learns it; he, however, begins with serious gaps in his memory, and so we will better understand the story if we follow in the order it happened instead of the order in which he discovers it.  He remembers being a helicopter pilot and team leader fighting with American forces in Afghanistan, and eventually remembers that he was in a serious disaster, taken away by medics.  He is not dead, but he does appear to be in something like a persistent vegetative state, with the lower part of his body absent and life support sustaining part of his brain.  He was in that sense kept alive.  In that state he was transferred to a division called Beleaguered Castle, where he is the prototype of a new weapon against terrorism:  they are able to send his mind into a moment in the past, where he can experience events as someone else, and so return to the present with information that cannot be acquired any other way.  He can, in effect, see who performed specific terrorist acts in the past and return to the present to identify the terrorist.

There are for him three realities, although he does not grasp this for some time.  He is in one when he is not active, which is a type of capsule with a video screen.  This reality does not exist at all, but is a construct inside his head.  The screen is his mind's way of handling the data which comes from Beleagured Castle, in the form of an audio video computer link usually to Captain Colleen Goodwin.  She gives him his mission briefings, helps focus his mind and memory, and receives his reports.  His body is in an adjacent room, unaware of its surroundings.

The third reality is much more difficult to grasp, in part because it is not what the program director believes it is, and in part because what it actually proves to be is the surprise twist in the film.  Whatever it is, when the equipment is activated, Captain Stevens' mind connects with the mind of a teacher named Sean Fentress, such that for eight minutes he is Sean Fentress in the last minutes of Sean's life.

Sean died this morning, on a train inbound to Chicago which exploded after passing Glenbrook Station while alongside an outbound freight train, in a major disaster.  For some reason, the bomber exploded the train so he could then announce that he would be detonating a nuclear device somewhere in downtown Chicago that afternoon.  Captain Stevens' mission is to identify the bomber by finding the bomb and from that the man who planted it in time for authorities to prevent the second bombing.

To this end, Stevens gets to relive the last eight minutes of Fentress' life as many times as it takes, using Fentress' body and his identity to manipulate events such that he learns what he needs to know.  He cannot change the past, they tell him, because what has happened has happened; they want that information so they can change the future.  He meets the people on the train and begins to care about them, most particularly about Fentress' traveling companion and co-worker Christina Warren, and it bothers him beyond measure that he cannot prevent them from dying in the impending explosion.

This opens many questions from many angles; but with our next article we will begin to explore what is supposed to be happening according to the people running the program.

Dr. Rutledge, who created the device that enables Captain Stevens to experience past events, explains how it works in one of the better pseudo-rational explanations in time travel stories.  It is not, he says, time travel, but instead a way of connecting Stevens' mind with the mind of one of the passengers on the train.  He suggests that our minds retain fairly complete data of the last eight minutes of our experience, and that that data survives briefly after death.  Because Sean Fentress' brain is very similar to his own, Colter Stevens is able to link to those memories and live them.

This is not entirely unreasonable, assuming that everything Rutledge says is true.  It might even be reasonably plausible for Stevens to focus his attention on details of which Fentress was unaware--the eye sees many things the brain does not process.  If the experience is a mental recreation of events from the memory of one of the passengers on the train, it is not even unreasonable that Stevens could manipulate it, something like a video game, getting different but predictable reactions from people based on Fentress' knowledge of them.  It would be a kind of simulation, something like we saw in Next or Minority Report, using the information available to produce the most likely outcome.

The problem is that no matter what Stevens does, he should not be able to discover anything that neither he nor Fentress actually knows.  Any such information is completely unreliable.  In the film he recognizes that the bomb came from behind him in the first time through, and it is not impossible for Fentress' memory to have told him that it came from "that direction"; but nothing in Fentress' memory would have told him the appearance of the bomb or how it worked, and any such information at that point would be based on probabilities and Stevens' knowledge of bombs.  To some degree, it is natural that he ought to be able to disarm it, because it must work the way his mind imagines such a bomb to work, and nothing about it tells him anything about the real bomb--or the real bomber, which becomes the second problem.  If he happened to get the information from the fact that the bomber said something within Fentress' hearing before disembarking from the train, that would be within the available knowledge; that is not the case.

There might be a way around this if we suggest some type of noosphere, or more accurately a collective unconscious; that is, if all minds are somehow linked so that all knowledge is part of a common pool and we individually draw our part from it.  Such a pantheistic concept is not without its adherents, and it would allow the possibility that by connecting with the mind of Sean Fentress that morning Stevens was able to tap into the universe through the knowledge of all persons then alive--including the bomber, who prior to Stevens was the only person to have any knowledge of the bomb.  Thus Stevens can find the bomb because he is tapping into the collective memory of everyone in the world at that moment, and from that recreating a simulated version of the world.

This does not seem at all to be within Dr. Rutledge's expectations.  That being the case, it is difficult to grasp how Rutledge believes Stevens can learn something Fentress could not have known.  The pseudo-rational explanation begins to crumble faced with this complication.  This pushes the viewer toward one of two conclusions:  either the entire premise of the show is foolish because you couldn't possibly build a machine that would do what Rutledge claims the way he claims and get the results he gets, or Rutledge is wrong and he has not built what he thinks he has.

We ultimately learn that Rutledge' machine does not do that.  What it does instead is to us far more interesting, and in some ways it works precisely because Rutledge does not know what it does.

If the device Dr. Rutledge uses to send Captain Stevens to the event did what he thought it did, it would not work.  Yet unbeknownst to the doctor, it does something entirely different--he has built a time machine, but one which works on a specific theory of time which normally would never produce any successful results for the time traveler.  As we said, it is because Rutledge does not know what he is doing that he succeeds.  He has created a machine which upon activation creates a divergent dimension, something like a parallel dimension but that it never existed prior to the moment the time traveler arrives.

Normally, for reasons discussed in The Two Brothers:  Why Parallel Dimension Theory Is Not Time Travel, a time travel machine which carries someone to another dimension will never be used.  The initial tests with inanimate materials will send those materials to another universe, and thus they will appear to have disintegrated entirely, and no person will ever be sent to the past.  However, this machine does not send a person to the past; it connects a person's consciousness with the consciousness of someone else in the past, such that for some period of time the traveler lives through the body of this other person, and then returns to his own universe with whatever information he gained.  Since no one believes he traveled to the past, no one expects there to be any evidence that he was ever there.  He cannot change the past because, as Dr. Rutledge rightly observes, he is not in the past--not, that is, in his own past, but instead in the past of a universe he created by his arrival, which is identical to his own except to that degree that he by his actions alters it.  As he does so, he also gathers the needed information, which is then brought to his own universe and used for the desired purpose.  We send our investigator to the past not so he can prevent the original crime, but so that in becoming a witness to the original crime he can give detectives the information they need to arrest the culprit.  No one expects him to prevent the crime or to have any impact on the past, because they only want the information from the past to use in the future.

Thus our time traveler is changing the past, but doing so in a new dimension.

This does not solve all the problems in the movie, but it does make for a plausible time travel story of sorts (if you accept that divergent dimension theory is time travel).  We accept up front that the usual anomalies do not apply as they would in replacement theory, because it is not Colter Stevens' past which is changing, but the past of some other Colter Stevens whose life is impacted but not relevantly so, since in this case it does not matter whether or not he makes the trip.  We will, however, have to look at some of those problems.

One of the more interesting innovations in time travel was popularized by the television series Quantum Leap, in which Dr. Samuel Beckett traveled to moments in the past by having his mind take over the life of someone else while they temporarily lived in his body in a small room in the future.  Something like that is happening in Source Code:  Captain Colter Stevens does not travel bodily to the past, but his mind or soul or spirit or some other intangible part of himself takes over the body of Sean Fentress.

What the film never asks is, what happens to the mind of Sean Fentress?

On one level we don't care.  Sean Fentress died when that train exploded earlier this morning, and since we are specifically told that those people are all memories having no reality we, like Stevens, take the view that they're not real, they have no minds or spirits or souls, and the fact that Fentress is not controlled by Fentress is not significant--Christina presumably is not controlled by Christina, either, but by Stevens' mind tapping the memories of Fentress.  Yet in the end we discover otherwise:  somehow the spirits (and bodies) of everyone in the world have been duplicated in this divergent universe.  The one exception is Sean Fentress, whose body is present but whose mind is missing.  Why was it not copied?  Or if it was, where did it go?

We are apt to miss the complication here, because to our minds the divergent universe began at the moment Stevens arrived, and so the fact that Fentress was not copied means only that we did not make a copy of his mind.  However, from the perspective of the divergent universe, they have always existed, and at some point Stevens arrived and possessed Fentress, disposing of his original self and controlling his body thenceforth.  People in that world have every right to say, as Christina once in jest says, What have you done with Sean Fentress?

In most iterations of the universe it is a question that will never really be asked.  Fentress dies eight minutes or so after Stevens possesses him; he would have died in any universe in which that did not happen.  Yet because in the final universe Stevens survives as Fentress, the question of what becomes of Fentress in that and every other universe must be asked; and it is not something the film ever answers.

One guess is, Fentress was sacrificed in the process of creating a new universe.  We know that matter and energy are neither created nor destroyed, but divergent dimension theory breaks this law of thermodynamics entirely, creating enough matter and energy to construct a duplicate universe.  We do not know how much matter or energy exists in a human spirit.  Some would suggest that as one of the few things in the universe that are eternal, they individually are infinitely greater than the entirety of the temporal universe.  If that were so, sacrificing one such spirit would provide sufficient energy to build a new universe--but not to create all the spirits of those who live within it, so in solving one problem it creates another:  how do we get the duplicate spirits for all those duplicate bodies?  If the answer to that is that spirits are merely byproducts of material functions, then the loss of one gives us nothing from which to build a universe--and forces us back to the question of how the mind of one person can possess the body of another.

We won't find the answer to this dilemma in the movie, because for most of the movie we are told that this is not a divergent dimension but an imaginary construct.  We have already noted some of the problems and inconsistencies in that, and we will uncover more as we continue.  What we know is that when Stevens possesses Fentress' body, he creates a new universe in which at that moment an alien consciousness (Stevens) possessed a body whose original consciousness (Fentress) at that moment ceased to exist, and in which everything else was as it had always been.  Perhaps Fentress is in Stevens' comatose body for the moment, and then dies either when he returns to his own body or when Stevens' body dies, but no one ever asks the question so no answer is ever offered.

Having concluded that Source Code deals in time travel under a divergent dimension theory model, it follows that each time Stevens travels to the past a new universe is created, a bit different from any previous universe.  The obvious question is how they are different and what happens in them.  The less obvious question is how many times the nuclear device explodes.  We will begin, however, with the first such universe, and proceed from there.

It appears that the first time the system activates to send Colter Stevens into the mind of Sean Fentress, Stevens loses all recent memory; he has no idea where he is, what is happening, or when it's over who Beleagured Tower and Captain Goodwin are.  Some of that memory is restored in the process, but in the first universe he is struggling with the realization that he is not himself.  In the original universe, Sean Fentress was as normal as ever until the train exploded; in this universe, he starts losing touch with reality--from the perspective of his companion, that is.  He does not know who or where he is, nor recognize people he knows on his regular commute.  Then the train explodes.  Perhaps someone who exited the train at Glenbrook station remembers that one of the passengers started acting strange, but in the short time available it is unlikely this information would be uncovered by anyone investigating.

What happens next in this world?  Since this world also has a Colter Stevens waiting for his first Beleagured Castle mission, and the train exploded and the bomber made his threat, in this world the other Colter Stevens will be activated.  We know that when activated, the traveler displaces the mind in Fentress' body, and thus there is no additional problem created by Stevens replacing his self in Fentress' body.  It is what the original Stevens is going to do in his own universe, repeatedly replacing Fentress and creating new universes.  The new Stevens will do the same, creating another universe like this one, in which his Fentress is confused and disoriented.  Then the new Stevens will make several more trips like those made by the first Stevens, and ultimately he will identify the bomber and report the information to Beleagured Castle, with the result that the nuclear device will not explode.

That pattern will be repeated in most universes:  as soon as the universe is created and the train explodes, they will activate their Stevens, who ultimately will identify the bomber by doing what we see, and so prevent the nuclear explosion.  The only worlds in which this clearly does not happen are those in which he prevents the train bomb from detonating and gives Derek Frost to the authorities, and obviously the nuclear device does not detonate in those worlds either.  For the second bomb to detonate, Stevens would have to alter the history of that world in a way which alters his doppelganger's knowledge, experience or identity.

Thus we learn two things from considering the first universe.  The first is that the larger bomb is unlikely to detonate in any universe, because every version of Stevens we have thus far predicted will ultimately identify the bomber.  The second is that this one event will result ultimately in a number of diverging universes expanding toward infinity, because each time Stevens creates that first divergent universe he creates a Stevens who will create another divergent universe, plus a divergent universe similar to every divergent universe he is still going to create, and so they blossom outward infinitely.

Despite the sheer number of such universes, the fact that they will match one or another of those we see means that we need not attend to them further, but can focus on those universes we see Stevens create.  The next of those is different in some ways, but not in any meaningful way.  Again we have regular commuter Sean Fentress suddenly acting out of character, claiming to be railroad security and trying to prevent the explosion by forcing people to deactivate electronic devices.  This time his odd behavior occurs after passing Glenbrook Station, so no one alive in that universe saw it.  It, too, will lead to that universe's Colter Stevens starting the same mission to identify the bomber.

Yet there is more to learn from those other universes our Stevens is going to create.

The third time Colter Stevens travels to the past, and thus in the third universe he directly creates, something happens which ought to make the thoughtful viewer balk, because if what Rutledge claims is happening is true the filmmakers made a glaring mistake.  However, Rutledge is wrong, and this seeming mistake winds up being the first evidence to that effect.

Stevens is told that he lives in Fentress' memories for the last eight minutes that Fentress was alive, but that Fentress died that morning when the train exploded, and there is nothing that can change that.  The bomb exploded at 7:48, and Fentress body, and his brain, were pulverized and incinerated by the blast.  He did not live more than an instant after that, and in both previous replays of events Stevens returns to his own body at the instant of the explosion, confirming this conclusion.

In this third world, Stevens sees the train explode, standing on a platform some distance from it.  He then has time to react, to lose his temper, to fly into a violent rage against the wrong person, and perhaps a minute after Fentress must have died to fall onto the tracks and be hit by the express train.

He dies, of course.  The thought might occur to us that Fentress dies because it is his time, so Stevens was certain to die.  Yet we are not thinking clearly if it does, even though that might be what the scriptwriter wanted us to think, because Fentress' time to die was a minute sooner.  In fact, it is shortly after this that Rutledge carefully explains to Stevens that Stevens cannot live in Fentress' world beyond that eight minutes, an explanation that ought to activate the alarm bells because he just did.

The only way Stevens can outlive the explosion as Fentress is if Rutledge is wrong, and Stevens is in a divergent universe.  It is not solved by having Fentress die in the next minute or so.  The correct outcome would be that the simulation ends, that Fentress, Christina, and everyone and everything else simply cease, like a snapped film or a video game freeze.  The moment the original Fentress died, the data stream would have ended, and the simulation would have ceased.  That it did not do so--that Stevens stayed with Fentress' body for another minute--tells us that Rutledge is wrong, that this is not a simulation created by connecting with the memories of a dead man.

There are not too many alternatives for what it might be instead, but we already have the answer to that from the end of the film so speculations are frivolous at this point.  On the other hand, the team back at Beleagured Castle ought to have noticed that Stevens did not return on schedule--and there are several other oddities about what is happening in the other worlds of Steven's life which bear some consideration.

We have been examining what happens in the worlds created by Colter Stevens' trips to the past, but there are also events occurring in the world from which he comes, and in the world his mind has created for him.

The first of these comes very early in the film, before we understand what is happening, and so we do not notice just how little sense it makes.  Stevens, transitioning from the exploding train to the capsule, complains that he is in an uncomfortable position with his head down.  Goodwin responds by saying she is adjusting rotation, and his seat changes position so that he is upright.  However, we later learn that the capsule does not exist--it is a construct of Stevens' mind which it uses to give him physical existence while communicating with Beleagured Castle.  His only physical existence is in a total life support chamber on a level table in another room.  There is no control on Goodwin's console that would alter the angle of the imaginary seat in the imaginary capsule no one knew he was imagining.  Yet when she says she is adjusting the rotation, his seat rights itself.  The only way we can guess that might have happened is if the suggestion that someone was adjusting the seat caused him to imagine that it was being adjusted; that, though, seems quite a gamble for Goodwin to take--she could not know that the suggestion would have the desired effect.

However, when he was killed by the express train there was something strange back in our world, and that bears consideration.  It appears that Stevens almost died.  We might have thought it was because Fentress was killed by the express train; but would that impact genuinely have been more traumatic than being killed in the explosion?  That is probably not the case.

What notably is the case is that when they send Stevens into Fentress, there is a timer running, counting down his last eight minutes.  When the bomb explodes, Fentress dies, and Stevens pops back into his own body in this world.  However, in this third time through, he got off the train, taking Christina with him, and lived a significant number of seconds beyond the explosion--but the equipment at Beleagured Castle is designed for him to return to his body at the exact second of the explosion, and he was not yet there.  Thus the most plausible explanation is that when Stevens stayed in Fentress' body, and the equipment hit its zero point, his own body started to die; and when a moment later he was killed he returned to an already unstable body and had trouble bringing it back to life.

That also explains why the capsule was "cold" when he returned:  his own body's life support was terminating, and he had to force life back into it.  He perceives it as a mechanical problem with the capsule in which he imagines himself; Beleagured Castle perceives it as his body dying.  He was not there to keep it alive when he needed to be, but he was back in time to get it working again.

To some degree, this also explains why, later in the flim, the suggestion that he might in some sense be dead causes the capsule to begin to collapse.  He has constructed an imaginary reality in which he perceives himself to be alive and corporeal within a technological simulator or transfer machine he does not fully understand.  The suggestion that it does not exist means that this body does not exist either.  The suggestion his perceived body does not exist means that he is not alive in any sense he would have meant by that statement.  The realization that he is not alive in terms he understands causes him to begin to die--to lose what grip on life he still has--which expresses itself as the collapsing of the imaginary construct surrounding him.

Rather cleverly, the film delays telling us that Stevens cannot live in Fentress' body past the eight minutes Fentress was alive until after we see him do so, and as previously mentioned hides this fact by the sleight of hand that he dies a moment later; but in this movie, dying and dying are two different things.

The fourth divergent universe is interesting because Stevens begins using his knowledge from previous trips to anticipate and manipulate events around him.  He avoids the spilled beverage, has his ticket ready for the conductor, and jumps ahead of the conversation.  He is stopped while trying to get the gun, and that's the end of that world for him when he again dies in the explosion.

It is in the fifth world that information starts flowing to him in ways that change his circumstances.  He learns that the patch on Goodwin's shoulder puts her at Nellis Air Force Base, and so knows where to find Dr. Rutledge.  He also learns, through Christina's smartphone, that he, Captain Colter Stevens, was reported dead in combat in Afghanistan, that he saved the life of one of his men (Sargeant Robert Alvarez), and that his father Donald received the Silver Star awarded to him posthumously.  It is this latter information that leads to his confrontation of Goodwin, demanding to know whether he is or is not alive, and the consequential weakening of his imagined reality.

This time, though, he places a phone call to Nellis Air Force Base and leaves a message, including his real name, for Dr. Rutledge.  This is the first time he has done something as Fentress that might alter events for the Stevens in the newly created universe.  Up to this point, he either died (along with nearly all witnesses) on the train or was killed immediately thereafter, with his actions easily attributed to his distress over the realization that there was a bomb on the train.  The call to Dr. Rutledge, though, is entirely different.  We have to assume that Rutledge gets the message, that the man who is at that moment lying barely alive with half his body missing on a life support table in a room in his offices placed a phone call to him that morning.

Of course, Rutledge could dismiss it as a prank:  someone who knew the identity of their top secret subject called pretending to be him.  This Rutledge does not know that he lives in a divergent universe created when a divergent self sent a divergent Stevens into the body of Sean Fentress on a train moments before it exploded, and he believes that time travel is not possible and that even if he does send Stevens to "the past", Stevens can't call him.  However, moments after the call is logged (and the times of these events will be logged accurately) a train bombing occurs, and the bomber warns of a coming second bomb in a way which launches Beleagured Castle into its first mission--sending Stevens back to that time.  It could begin to fray the edges of his conviction that the world to which he sends his investigator is completely unreal.

That creates unpredictable results, because it means that in that universe Rutledge is changing, and that means his interactions with everyone, and particularly with Stevens and Goodwin, are also changing, and that their situations are correspondingly altered.  To this point we knew that every universe Stevens created was similar enough to the original that we could predict identical universes being created from each of them.  Now suddenly it is possible that Rutledge will do something different which will mean Stevens will do something different, which means that there might be a world we did not predict.

That problem escalates if it starts small and does not have any impact immediately.  That is, Rutledge was told that Stevens called, then he realized that he was sending Stevens to the past, but he considered it a coincidence.  If it does not change anything this Stevens does as Fentress until his fifth trip, then when he returns and informs Rutledge that he made that call, Rutledge will already have received it that morning and will be forced to confront the change.  At that point he either arrogantly assumes that he is right, or he changes his strategy; and if he changes his strategy, we may have worlds we did not wish to have.

When Stevens leaves a message for Rutledge, he begins a change which could have serious repercussions, as Rutledge might change his actions which would result in Stevens changing his actions and different worlds resulting from it.

Let us suppose that Rutledge realizes his mistake before he sends Stevens back, and that after the first trip Stevens gets the explanation, not that this is an imaginary construct based on memories from a dead victim of the crash, but that he is traveling to divergent universes, creating history in another world.  On that assumption, he really could prevent the train bomb, and he could do so without catching the bomber, and without getting himself killed.

However, it appears that the mechanism that returns Stevens to his own body is the death of Fentress.  Rutledge thinks it's his machine, but we already know better because we saw Fentress survive the explosion only to be killed by the express train a moment later.  If Fentress is not killed soon enough after the time of the explosion, the body of the Stevens who is in him dies, and Stevens remains in Fentress' body in the other world.  He never returns to report what happened.  In that world, they lose their traveler, and then never learn who the bomber is, and the second bomb destroys Chicago.  Meanwhile, in the world where Stevens saved the train, the bomb never destroys the train, the Beleagured Castle program is never activated, and again the second bomb destroys Chicago.

That's two universes in which Chicago lies in rubble, because Rutledge did not attempt to persuade Stevens that his experiences were not real in any real universe.  And, as we already observed, any universe that is created once in this story is created an infinite number of times.  That one tiny change in reality has potential consequences of a devastating nature.

Further, it does not matter in which universe Stevens saves the train.  As long as Fentress does not die, Stevens does not return to report; if he does not return to report, they do not stop the bomb.  Stevens is already on the edge of believing these worlds are real, and if Rutledge is not certain they are not Stevens will try to save the train, and ultimately will succeed, which means he probably will not be killed until the other bomb explodes later that afternoon, by which time his body in the original world will already be dead and the bomb he was supposed to help stop would have been detonated.

We do not see these worlds because we never see the world from which Stevens is sent and Rutledge receives the call.  However, the probability that that pairing of events will result in nuclear detonations in two resulting universes, and in duplicates of those as the changes propagate beyond them, is very high, suggesting that they certainly do exist.  The one consolation we have is that had the Beleagured Castle program not been launched, there would be only one universe, and in it the train would have exploded in the morning and the city of Chicago that afternoon.  From that perspective, although the phone call resulted in an infinite number of universes in which Chicago was destroyed, that would have been the default outcome, and Stevens efforts ultimately resulted in a greater infinite number of universes in which Chicago was saved--a universe that in one sense would not have existed without him.

Captain Colter Stevens' sixth and seventh trips to the past are presented in such rapid blurred flashes that it is difficult to be certain what the filmmakers are attempting to communicate to us.  Did he spend the same eight minutes on the train, accomplishing nothing more, spinning his wheels not getting closer to the answer, and they are conveying to us that he made "several more" trips to no avail?  Is it rather intended that we should think his own resistance to the Beleagured Castle program resulted in the failure of him to connect to Sean Fentress' mind at all, or to create additional universes?  The most we can say is that they tried to send him back again, more than once, and that they were not getting the information they needed.  If they were creating more universes, we know nothing of what happened in them, nor how many there were.  Ultimately, though, they play a recording of Stevens' father talking about his son's heroism and the father's pride, and that puts him back in focus.  This time he succeeds.

He has a funny way of succeeding, really.  He gets Fentress shot.  He gets Christina shot, also, and the bomber blows up the train and takes his bomb into Chicago.  However, as we already recognized, in this universe, too, another Rutledge (one who did not receive a phone call) will send another Stevens to start the process with another Fentress, and ultimately that Fentress will be dying beside an identical van in an identical universe, and will return to this universe to give the same information to that Rutledge.  So this universe, too, will prevent the destruction of Chicago, even though it suffered the destruction of the trains.

Still, he takes his information back to his Beleagured Castle, and they use it to snare their bomber and save their Chicago.

Stevens had bargained with Rutledge before making that last trip, promising to give him what he needed if Rutledge would then let him die.  Rutledge now wants to renege on that deal, and thinks he can do this with impunity because the system gives him the power to erase Stevens' memory.  He gives the order that this should be done.  Goodwin, though, has a sense of soldier's honor, that a promise to a comrade in arms ought to be kept, and no matter how it is that he did it, Stevens was the hero who did the job and ought to be commended.  She keeps Rutledge's promise.  However, Stevens wants it to be a bit more complicated:  he wants to die trying to save the people on the train.  He wants his eight minutes as Sean Fentress one more time, so he can do it right, catching the bomber and saving the people on the train.  She agrees, activates the system, and manages to shut down his life support in the last seconds as Rutledge attempts to prevent her.

Given everything that we have said in this series to this point, perhaps we ought to have guessed what would happen next.  As we noted at the beginning, however, the biggest surprise is that Rutledge was wrong, these are diverging universes created by Stevens' arrival, and they are real and continue beyond the moment they were expected to end.  We cannot say with certainty, but since the Fentress in this last universe manages to defuse the bomb, catch the bomber, and report the other device so it would be found, it is probably the fact that he was not killed that resulted in the death of the Stevens body back in the other universe; Colleen Goodwin mistakenly believes, and her superiors mistakenly believe, that she killed him when she terminated his life support at his request, but given what we already know from the third trip, he would have died anyway.  As long as the body of Sean Fentress remained alive in the new world, he would remain in it.

Goodwin will face a Court Martial, but given that Stevens was already a war hero who technically already died for his country, and who everyone in the project will have to admit suffered the experience of death (even if only in his mind) several times during this covert mission with every expectation that he would do so again as long as he remained in the program, and the revelation that he specifically asked to have the support terminated and Rutledge specifically agreed to do so and then reneged, she will probably receive a reprimand and a transfer to another assignment.  Rutledge might also receive some kind of scolding, but it appears that he is not military, and the Courts Martial have less authority over civilian employees.

We still must look at that last world.

As Colter Stevens becomes Sean Fentress (or is it the other way around?) one final and this time permanent time, he puts everything together.  He removes both remote detonators from the bomb, handcuffs the bomber to the train, alerts the authorities to his presence and to the bomb in the van, gets closure with a phone call to his father, has the comedian Denoff entertain the people in their railcar, and with half a minute to spare tells Christina that he has decided to kiss her again--she reacts to the "again", and she's not likely to forget it, because although he has kissed her, her doppelganger in another universe, she has never kissed him.

Then the unanticipated happens:  the world does not end, and Fentress does not return to being Fentress, but becomes Stevens' new body in his new universe.

There are a few quirks, however.

The most obvious one is that Stevens sends Goodwin a text, shortly after the disaster does not happen, identifying himself and informing her that their team was responsible for the capture of the bomber which only now is being reported on the television.  She wisely decides not to inform Rutledge; but she knows now not only that it works, but that it does something--not exactly sure what--different from what the inventor believes.  That will influence what happens when in this universe there finally is a perfect opportunity to activate Colter Stevens and send him into the past to gather needed information to prevent a disaster in their future.

The bigger problem, though, is that Colter Stevens is going to have to become Sean Fentress.  He knows nothing of Fentress' life--has never been to his home, does not know whether his parents are alive, has never met his colleagues or his students, would not recognize stories from his own past.  Complicating it, he has initiated a serious relationship with a twenty-eight year old girl who already knows Sean Fentress--she works with him and commutes to work with him.  Even in the eight minutes of their relationship she has already noticed that he is different.  Stevens is not going to be able to maintain the deception and the relationship.  At some point he is going to have to explain to Christina Warren that before that fateful train ride he actually was Colter Stevens, the helicopter pilot who was reportedly killed in action but was actually transferred in a seeming vegetative state to a top secret program which sent him into Fentress' mind in order to gather information and prevent the bombing in that other universe.  This is going to be difficult; he has no way to prove it, and the more he tries to prove it the more he risks being identified as a security breach.  Yet he cannot maintain the relationship with Christina Warren without revealing the secret to her and getting her to believe him and accept him as who he is.  There are a lot of ways that can go; all of them are different from the universe in which he died on a table in a lab after delivering information from the past.

He has a bright future if he can fool the people he needs to fool and gain the confidence of those whose confidence he needs to gain.  It is a tightrope, however.  He cannot go back to being a helicopter pilot because Fentress does not have the credentials and if he reveals to the military that he is Stevens Rutledge will deny it.  He has no training as a teacher of whatever subject Fentress teaches and is going to have to be good at it fast if he's going to avoid losing the one job for which he is credentialed.  He also has to figure out how to deal with all the friends and family he never met, and what if anything to do about his own friends and family who never met him.  However, if he can persuade Christina, she can probably help him with the rest.

In the end, the movie works and breaks several of our time travel expectations.  It proves that you can build a divergent dimension travel time machine if you do not realize that's what you have and you are using it to send and retrieve someone investigating events in the past.  Certainly your observations change history, but it's not your history, and if you are careful and attentive enough you might be able to learn what happened before you changed it and never realize that you are creating worlds with new histories.

It is rare to find a time travel movie that works as well as this.  Kudos to the creators.