Primer (2004) : Movie Plot Ending Explained

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Primer is a long lost movie that only has a cult following. It was made by Shane Carruth who also wrote the story and acted in it. He also produced it, edited it and worked on the production design. Heck, he even did the music for the film. He also had a pea-sized budget for the film. No CGI, no nothing. Yet he happened to create one of the most complex time travel movies which demands a 6-page explanation with timeline diagrams. Shane Carruth’s second film was Upstream Color which was a pretty cool concept too. This article is going to be a fully textual explanation because the diagrammatic representation of the timeline will need to be in 3 dimensions. Actually, I’m being lazy to create one but I have thrown in one timeline diagram in-between to explain the dynamics of Primer’s time travel. Here’s a detailed plot analysis and the ending of the film Primer explained, spoilers ahead.

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Here are links to the key aspects of the movie:

The insignificant bits in Primer:

The movie starts off with 4 friends who work on side projects apart from their day jobs. Aaron, Abe, Robert, and Phillip are the 4 people. Ignore Robert and Phillip, they will go away soon. We care only for Aaron and Abe and the multiple instances of them in time we will try and follow.

Primer Explained: Story gets going

After a fall out, Abe and Aaron decide to team up on an invention that aims at reducing the gravitational effects on objects. In effect, reduce the weight of objects. However, things don’t go according to what they envision.

Abe meets Aaron on a park bench one morning and explains to Aaron that if he skips work, Abe will show Aaron the most important thing that any living organism has ever witnessed. Abe shows Aaron the object that has been in the machine for mere days but has protein build up that happens over many years. Abe gets Aaron to put a watch in the machine to see the time lapsed for the watch. Abe wants Aaron to confirm the findings.

They basically end up creating a device that sends the object put inside it back and forth through time. They also notice that the objects tend to make around 1300 trips back and forth. The explanation to this is not given attention to, something about probabilities that lead to exits from the time loop only after a minimum of 1300 loops. Abe then explains the A-to-B loop.

A to B Loop

Primer: Explanation of A -> B that is drawn on paper

When the machine is turned on for a period of time, say 1 min, the object put inside it after 1 min starts going back and forth in time. If the machine was started at 12:00PM and the object is put inside at 12:01, the object travels back to 12:00PM and then back to 12:01PM. It keeps looping in this manner about 1300 times before it moves forward past the 12:01PM time. When the object is taken out soon after 12:01, it has already spent over 2600 min (because of the back and forth – 1300 x 2) inside the machine.
12:00PM is the A end.
12:01PM is the B end.

So the watch thrown in at the A end and Taken out on the B end, travels a total number of trips from A to B to A to B to A …. and finally to B. The total is odd.
If the watch is thrown in at the B end, it travels a total number of trips from B to A to B to A … and finally to B. The total is even.

Primer: Time Travel Works

Abe tells Aaron how the machine seems to work, also adds that if the object was smart, it could enter at the B end and calculate an exit at the A end. This means that the “smart object” can travel back in time. Smart object being – a human being. Abe proceeds to take Aaron to a location and tells him what Aaron was going to witness was not a prank or a practical joke of any kind. Abe hands Arron a pair of binoculars and Arron sees another Abe walking in towards the building with an oxygen tank. Basically showing Aaron that the Abe has already travelled through time.

primer main characters

Primer: Explanation of the Time Travel

Classically, we are used to instant time travel. Person at time t1 just gets transported instantly to time t2 (like say in Predestination, Looper or Timecrimes). That is not how time travel works in Primer. To travel back in time here’s what one has to do:

1) Start the machine at a time t1 (the A end), say 12:00PM
2) Wait for the machine to run, say 6hrs. Buy an oxygen tank.
3) Get into the machine after letting it run for 6hrs, this will be time t2 (the B end)
4) Be in the machine for 6hrs, while in the machine you are travelling back in time. You are travelling back at the rate of 1 min per min of your watch. So set your watch’s timer to 6hrs.
5) Use the oxygen tank to help you breathe for 6hrs in the box.
6) When the timer runs down to zero, it’s time to exit the box. When you exit the box, you will exit back at the A end, which is time t1, which is 12:00PM.
Unlike other time travel movies, you cannot travel to a point before the machine was turned on. The time travel window is limited to when the machine was turned on.

What’s the deal with the 15min timer on the machine?

Imagine you exit at the A end at time t1 which is 12:00PM in the above scenario (step 6). You will run into your past self who would be turning on the machine (step 1).
Running into your past self is not a good idea so you set a timer of 15min on the machine. This ensures that step 1 will happen 15min after you turn on the timer. This gives you enough time to get out of the area and your future self will not run into you.

Note: if you happen to exit the box before reaching the A end, then the chances of your brain getting fried is high. We’ll get back to this later.

Primer time travel explained

Primer: All Timelines Explained

Aaron is mind-blown, realizes that the Abe he’s been with all day is an Abe from 6hrs into the future. The Abe he sees using the binoculars is the Abe from the present timeline. Aaron asks Abe what he did prior to entering the machine at the B end. Abe explains that after starting the timer, he checked-in to a hotel and disconnected from the world, no phones, no TV, no nothing. After 6hrs, he went back to the machine and got in.

Now we start counting timelines, every time someone travels back in time, it leads to a new timeline. The events in a timeline may not be different from another but it’s a new timeline nevertheless.

Primer Timeline 1:

Abe starts the machine, drives off in his car and checks into a hotel. Aaron is undisturbed so ends up going to work (They talk about this, but is not shown in Primer). Abe checks for stock prices and returns to the storage facility 6hrs later and enters the machine at the B end.

Primer Timeline 2:

Abe exits the box at the A end, is without a car and takes a taxi and stops Aaron from going to work, the two of them watch the Abe from Timeline 1 entering the storage facility using binoculars.

Aaron now wants to do exactly what Abe has done. They work on another box for Aaron and the next travel is set up – perhaps the next day. Both Aaron and Abe go to the storage facility, start the timer and head to the hotel room. They check-in and stay there. They look into stock prices so that when they go back in time, they can trade on the right stocks to make money. They return 6 hours later to the storage facility and get into their boxes at the B end.

Primer Timeline 3:

Abe and Aaron exit back in the morning. Aaron exits a little soon so he gets a zap. They go back and start filling in the life of Aaron and Abe who are in the hotel room. They know which stocks to buy and they buy.

Later another day, in the evening, Aaron and Abe are talking about what they want from their lives. Aaron mentions how he would go meet his boss, punch him in the face and then go back and tell himself to not punch the boss. That way, no one would get hurt, the incident wouldn’t happen but he would get to feel how it is to punch his boss. Abe tells Aaron that he can NOT do that, no changing history; it would lead to a paradox. Aaron’s wife also asks if Aaron called the pest control she feels there are rats in the attic. We’ll come back to the rats in the attic.

They go through their following days doing the time travel thing; we’ll ignore those timelines that they end up creating, nothing major there. They continue to make money off stocks. They also decide to not tell the other two friends Robert and Phillip. So you can’t continue to fully ignore Robert, Phillip can be ignored. On one of the days Aaron bleeds from his ears, it’s perhaps from all the time travelling.

On the night that Abe and Aaron do their first time travel, Robert throws a birthday party and Rachel’s ex-boyfriend walks in with a shotgun over an argument that they are having. Aaron intercepts Rachel’s boyfriend and saves the day. One morning Robert tells this to Abe. Abe is angry with Aaron for putting his life on the line without caring for his wife and kid. Abe mentions that Rachel is stupid to get into those scenarios. Aaron explains how the whole time travel was fresh in his head and he was not going to let Rachel’s ex scare people like that.

They continue time travelling the next day. They start the timer and head to the hotel room. When they are in the hotel room, Aaron gets a call because he forgets to switch off his mobile phone. He takes the call. Talks to his wife and hangs up. They get to the machine and enter the B end.

Primer Timeline 4:

(ignoring the multiple other times they may have traveled back, there is nothing eventful and the timelines are not altered from the original by much):

When they travel back to the start of the day, Aaron’s phone rings as it’s still in his pocket. Aaron doesn’t pick and this is a cause for worry, breaking the symmetry. They check to see if each other is feeling fine.

Explanation for the mobile phone bit:

On that day, let’s say Aaron and Abe start the timer at 11:45AM for 15min and leave to the hotel. At 12:00PM, the machine starts up. When in the room, say at about 2:00PM, Aaron gets a phone call. He picks it up. At 6:00PM, Aaron and Abe get into their machines and travel back in time to 12:00PM. Now, when they reach the 2:00PM time, Aaron’s (who’s travelled back) phone rings.

The concept of phone towers is that when a call is made to a phone number, a grid wise search for that phone is done, the first grid that finds the phone, rings the phone. Since the Aaron on the street has received the call, Aaron in the hotel room, would not have received this call, hence that talk with his wife wouldn’t have happened. That is the break in symmetry. But the call is not a very important one and hence doesn’t alter the timeline drastically.

Messing With Paradoxes:

That night, Aaron and Abe are woken up by a bunch of brats whacking cars with sticks setting off car alarms all over the road. They both stand in the kitchen and talk. Abe suggests an idea to mess around with a paradox. Abe and Aaron can leave right now to Aaron’s boss’ house, punch him in the face. Then get in to their boxes and travel back to the point in the night when the kids are whacking the cars. They scare the kids away. This will ensure that they are not woken up, they never have the conversation they are having, they would continue to wake up in the morning and prep the box and travel the usual 6 hrs. This action however would leave two sets of Aarons and Abes in the next timeline. But they don’t talk about that, the paradox is what they want to mess with. Aaron asks Abe how they are to travel back to this point as the machine is not on. Abe admits that he did leave the machine running at 5:00PM. So the two of them set off to experiment.

On way to the storage facility, they notice Rachel’s dad in a car sitting and just staring away. Aaron mentions that earlier in the day, her dad was all clean shaven, but this one in the car had a 3 day stubble. This means that the guy in the car has travelled back to this timeline. They call Rachel’s dad’s home number and he comes on the phone. This confirms that the guy in the car is from a future time. They chase him down, and Rachel’s dad from the future eventually faints. They take him home and stash him in the guest bedroom. Abe and Aaron go to the facility to see if the machines are fine, and they are. They start questioning each other if they ever planned on telling Rachel’s dad about the time machines. They both deny of having any such thought. They think of a hypothetical situation where there is an emergency, but they can’t point a finger to anything. The permutations were endless. It looked like he exited the box too quick and that ended up zapping his brain like we had mentioned before.

Rachel’s dad-from-the-future was in coma and vegetative. Abe worries about what he may have changed. For instance, if they didn’t see him sitting in the car, they would have been at the boss’ house punching him in the face. But instead they are at home talking about the comatose dad. Aaron feels nothing much could have changed. No further explanation is given to how Rachel’s dad may have used the time machine. The point of focus is that, the timelines are being terribly messed around with and that scares the daylights out of Abe.

Abe decides that the consequences of this time travel is just too dangerous. He tells Aaron about another machine which Abe has left running from before his very first time travel. This is referred to as the Failsafe. Abe’s Failsafe has been running from the very beginning. Abe plans on inducing a long-ass sleep and going back all the way to the beginning and stopping himself from ever travelling through time. That way everything would go back to being how they were supposed to be and will revert to Timeline 1. No time travel, no problems.

Abe aaron

Primer Timeline <???>

Abe uses the Failsafe and goes back to Timeline 1 or at least he thinks he is. He drugs the original Abe from the timeline in his sleep. This ensures that his original self from the timeline doesn’t travel through time. After that, Abe-from-the-Failsafe lands up on the park bench to meet Aaron. His plan is to have a general conversation with Aaron and let him go to work. That way neither Aaron or Abe from the original timeline do their first time travel and everything will be undone. But the long-ass time-travel in the Failsafe has made Abe weak. What he also notices is that Aaron continues to have the same conversation they have in Timeline 2 regardless of what Abe says. As Abe falls to the ground, it is revealed that Aaron on the bench is simply following a recorded conversation that they had from Timeline 2. This means that Aaron is also from the future and is simply trying to re-act a conversation already had between him and Abe. Therefore this is not Timeline 1 or Timeline 2, this is some sort of an altered Timeline ???. We’ll get back to which timeline this is.

After Abe-from-the-Failsafe wakes up, he wants to know how this has happened. Aaron explains how he noticed the storage facility manifest having two rooms under the name of Abe. How Aaron already found the Failsafe machine. How Aaron realized that this was the “re-set everything” box. How Aaron didn’t like this.

Primer Timeline 1.1

Aaron decides to travel back in time using the Failsafe box (before Abe) right to the beginning. However, he takes with him collapsible version of the box with him back to the beginning. Taking back collapsible boxes back also means that he can end up doing more rounds of time travel in the same time window. If there was only one box, it can only be used by one person between the A end and the B end. This is because between the A and the B end, the machine has the person in it and can’t be switched off; it can kill the person inside, the person is inside is yourself, you don’t wanna kill yourself. Taking a box every trip back will give the ability to setup another machine once you exit. This gives the ability to do another trip back using the extra box.

Aaron, after using the Failsafe, drugs the Aaron of the original timeline (drugs the milk carton). This drugged Aaron is the person who is supposed to be on the park bench. But instead, he’s drugged and thrown in the attic. Remember the rats in the attic? That would be this Aaron, the first and original Aaron. Aaron-from-the-Failsafe now replaces Aaron-in-the-attic on the park bench (we never see this in Primer, it is inferred). He also decides to record all the conversations of the day. Important thing to note here is that this Aaron-from-the-Failsafe is the one narrating the story. He says “And that’s where I would have entered the story. Or exited, depending on your reference”.

Primer Timeline 1.2

Aaron-from-the-Failsafe, the narrator Aaron, uses the extra box to travel back again to the start of the day. Aaron-from-the-extra-box tries to take down Aaron-from-the-Failsafe (who has drugged the original Aaron). Aaron-from-the-extra-box has travelled a lot in time and is tired and is unable to subdue Aaron-from-the-Failsafe. However Aaron-from-the-Failsafe and Arron-from-the-extra-box talk it out. Aaron-from-the-extra-box has already lived the day and has recorded the events of the day, this is what Aaron-from-the-Failsafe was planning to do (and he does that in Timeline 1.1). Aaron-from-the-Failsafe understands that Aaron-from-the-extra-box has accomplished more in their common goal, hence Arron-from-the-Failsafe leaves.

Aaron-from-the-extra-box now encounters Abe-from-the-Failsafe while on the park bench, listening to the conversation that should have happened as per Timeline 1.1. But Abe faints instead. Timeline ??? from above is basically Timeline 1.2 and is what can be seen in the movie. And that is why we hear a recording of the dialogues from the ear piece. The recording is from Timeline 1.1.

Primer: What is Abe doing in Timeline 1.2?

Why hasn’t Abe gone back all the way to the beginning? After all he did use the Failsafe.
Aaron who uses the Failsafe before Abe decides he’s going back to the start. After Aaron uses the Failsafe, he also ensures he puts in a duplicate Failsafe in place of the original Failsafe. Let’s call the original Failsafe as Abe’s Failsafe. This is replaced with Aaron’s Failsafe. While Abe’s Failsafe is running all the way from the beginning, before any of the time travelling, Aaron’s Failsafe is running from a few hours after Abe’s Failsafe. These few hours is given so that Abe won’t notice that the machines have been switched. The few hours’ gap is also enough for Aaron to drug his past-self and get to the park bench and pretend.
Abe is not aware of this switch that Aaron has done. Abe is not aware that Aaron has used Abe’s Failsafe either. Abe thinks he is using Abe’s Failsafe but ends up using Aaron’s Failsafe instead. Abe ends up arriving a few hours after Aaron. By then, Aaron has already created Timeline 1.1 followed by a Timeline 1.2 – where he’s on the bench listening to the conversation over earphones.

In Timeline 1.2 there are 3 Aarons

1) The original Aaron from the timeline who is drugged and dumped in the attic.
2) Aaron-from-the-Failsafe who decides to go away, the narrator.
3) Aaron-from-the-extra-box who is on the park bench listening to conversations on the earphones.

In Timeline 1.2 there are 2 Abes

1) The original Abe from the timeline who is drugged and dumped in a bathroom.
2) The Abe-from-the-Failsafe who comes to the park and faints.

Abe-from-the-Failsafe comes back to consciousness and Aaron-from-the-extra-box explains how he discovered the Failsafe and did the switcheroo (basically everything that is described above). He also gives Abe-from-the-Failsafe the recording and goes down to the basketball court to talk to Will.

Will’s cousin is Rachel’s boyfriend. According to the original timeline, Aaron ends up inviting Will and his cousin to Robert’s party. So Aaron-from-the-extra-box invites Will as per the original events, the only change is that he misses shooting the basket which changes the conversation a little but doesn’t change the outcome.

Aaron-from-the-extra-box also convinces Abe-from-the-Failsafe why he needs to invite Rachel to the party. Abe-from-the-Failsafe finally agrees and calls Rachel to Robert’s birthday party.

Here is an unknown element. Aaron-from-the-extra-box may have gone back over and over to the start of the day to relive the day, to ensure that the events in the party go as planned. Which also means that more and more Aarons are hanging around in this timeline – no mention is made of what all the Aarons are up to. Finally, the scene in Primer shows an Aaron with Abe from the Failsafe at the party working to perfection. How many times has Aaron-from-the-extra-box gone back? Three? Four? Twenty? No idea. However, in the movie we see the party scene with a Final Aaron. We’ll call him Aaron-the-Final.

At the party, they open the car and sabotage the ex’s shotgun by removing the bullets. When the moment of conflict happens, Aaron-the-Final springs to the gunman (the ex) and saves the day.

The next scene is at the airport. Aaron-the-Final and Abe-from-the-Failsafe are talking about what happens next. Aaron-the-Final says they (Aaron-the-Final and Abe-from-the-Failsafe) don’t belong to the timeline they are in and they should just flick the passports of the original Abe and Aaron and just leave to another part of the world where no one knows them. Aaron-the-Final also suggests that they can make a copy of his wife and kid and leave with them.

Abe-from-the-Failsafe is annoyed with Aaron-the-Final and asks him to leave and never come back. Abe-from-the-Failsafe plans to sabotage the efforts of the original Abe and Aaron in creating and using the time machine. Abe-from-the-Failsafe hopes that the original Abe and Aaron will give up and move on to other projects. Aaron the Final leaves.

Primer Ending Explained: Timeline Unknown

The end of the Primer shows an Aaron in a place building a gigantic version of the machine. We can only assume that this is second Aaron from Timeline 1.2, the narrator, the Aaron-from-the-Failsafe. It is left open-ended, there is no closure given to the multiple Aarons and Abes that have been spawned. While some of them might cease to exist because of alterations in the timeline, others can cause further mess-ups to happen to create even more complex timelines. We don’t know, we never will.