Warning: This is an attempt to fully explain the movie Primer. If you haven't seen it, stop here. If you want to figure it out for yourself, stop here.

Also, I wrote this as a stream of consciousness after the second viewing of the movie, so I haven't vetted it for clarity. I probably made some assumptions about things that may not be 100% clear in everybody's mind. Let me know..

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Note: Abe2 will designate the Abe that has gone through the original failsafe machine. Aaron2 will designate the Aaron that has gone through the failsafe machine that he smuggled back through Abe’s failsafe machine & started immediately. If that doesn't make sense, don't worry; read on.

Abe, Aaron, Robert, and Philip are working on startup ideas in Aaron’s house. Aaron has a new fridge with a red bow around it. Did he buy this using future time machine earnings? No, because the machine hasn’t been invented yet and you can only jump back to when the machine was started. During this talk, Philip mentions someone named Platt; Aaron is upset when he hears this; it’s a reference to some VC or somebody that screwed them a year ago; keep this name in mind, though.

Abe and Aaron notice interesting gravity-reducing characteristics of their machine. They decide not to share this w/ Robert & Philip.

Aaron calls Abe one night to go to Aaron’s house to work. The call wakes Abe up in his bedroom, where he’s passed out & has a beard. He didn’t have a beard in any previous scene. Before Abe opens his bedroom door, he practices saying “Hi, Brad.” He opens the bedroom door, sees Brad his roommate and says “Hi, Brad.” Does he do this practicing because he’s really Abe2, the Abe that’s already gone through the failsafe machine & started everything over? Doesn’t seem right because again the machine hasn’t been invented yet.

Aaron says the machine is stable. Aaron and Abe mess with it and notice that it runs itself w/o batteries. They go to a steak dinner & discuss all the implications.

They go to parties to try to get VCs to fund them. At one party, they are shown talking to Thomas Granger, the father of Rachel, who is Abe’s girlfriend at the time. Somewhere in this time, Abe puts 2 time machines in one storage locker, and 1 failsafe machine in another. He turns on the failsafe. The failsafe is supposed to be a secret; Abe will use it to reset everything if something goes wrong.

(not shown in the movie) One morning, Abe sets a timer to turn on a time machine 15 minutes after he leaves the storage area. He then goes to a remote hotel & cuts off all communication w/ the outside world. In the early afternoon, he leaves the hotel, asks his broker which stock went up the most that day, then goes to the storage locker at 3 PM & enters the time machine. He travels a few hours back to the point when the machine went on (15 minutes after he left that morning).

Aaron2 is sitting on a bench with an earpiece in his ear. Abe looks at him from a rooftop, then goes down to talk to him. Abe thinks this is Aaron, not Aaron2. Abe tells him that he’s about to show him something extraordinary. In this scene, Aaron2’s speech seems strange because he’s just echoing what he hears in his ear, a recording he made before going through his failsafe machine. Aaron2 is trying to change the future as little as possible.

Abe drags Aaron2 along to the lab & whatever to discuss the protein growth. He demonstrates the watch traveling through time. Just before 3 PM, Abe takes Aaron2 to witness Abe going into the locker at 3 PM.

Rachel calls Abe in the car.

Abe and Aaron2 do this day-jumping a few times to earn money on mid-cap stocks that move during the day. They do their research in a different town’s library to avoid running into anyone they know & altering the future.

(not shown in the movie) Aaron goes to a basketball court & tells Will to bring his cousin (Rachel’s ex-bf) to Robert’s birthday party. Aaron has no ill intent other than mild mischief; he doesn’t know that Will’s cousin will threaten Rachel yet.

(not shown in the movie) Robert has a party and Rachel is threatened by Will’s cousin (an ex-boyfriend) with a shotgun. Aaron2 and Abe were not at the party. Rachel is not harmed, and Will’s cousin is not arrested.

Abe, Aaron2, and Kara (Aaron’s wife) are at Aaron’s house. Kara complains about rats; Aaron2 says don’t worry but really this is Aaron stuck in the attic. They are asking Kara what she would do with tons of money. Kara says “oh good things” but Aaron2 says “I’d go punch Platt in the face. But only if I could go back and make myself not do it, just so I could experience it.” Abe seems upset; he says “Aaron you can’t do that” because Abe is deathly worried about causality.

Abe knows that he has a failsafe machine, but he doesn’t know what happens if you travel back more than a few hours, so as an experiment he starts a machine at 5 PM instead of in the morning as usual. In the middle of the night, a kid runs down his street & sets off car alarms, including Abe’s Maxima. This wakes up Abe. Abe goes to Aaron2’s house & says, “now’s your chance to go punch Platt; we’ll go & do it, then come back & prevent the kid from setting off the alarms, so in reality it never happened, yet we experienced it.”

Aaron2 and Abe drive off to do it, but they notice that Thomas Granger is following them. Aaron2 says that he saw Thomas earlier in the day & he was clean-shaven, but now he has a 2-3 day beard. Abe is rattled so he calls his girlfriend Rachel to get Thomas’s number. He calls Thomas and Thomas is at home. That means Thomas2 is in the car behind them. Aaron2 chases Thomas2, and eventually Thomas2 falls into a coma (from misusing time travel & screwing himself up) and Aaron2 slips. Abe catches up with them and they take Thomas2 to a spare bedroom. The voiceover (Aaron2) says that this is when Abe decides to use his failsafe machine. Abe is worried that Thomas changed things that are unpredictable.

Abe takes the failsafe to start over.

Abe2 then oxygen-masks Abe in his sleep and puts him in the closet to take over Abe’s life (effectively).

We’re back at the scene where Abe2 meets Aaron2 on the bench. Funny: Aaron2 is saying what he said as Aaron, even though Abe2 is saying totally different things from Abe, so Aaron2’s conversation doesn’t make sense. Abe2 has just traveled a long way, though, so he passes out before having the same conversation with Aaron2 that he had before.

Abe2 goes to Aaron’s garage. Robert and Philip show up and say something that indicates to Abe2 that Aaron was at Robert’s party. But Abe2 knows that Aaron wasn’t at the party. So Abe2 figures out that even though he used the failsafe and everything should be back to normal, somehow Aaron interfered. The only way is if Aaron used a failsafe himself (he used Aaron’s failsafe).

They argue at the fountain while looking for a cat. As far as I know, this has no significance other than confusing the crap out of me at the first viewing.

Aaron2 and Abe2 discuss what to do about Rachel in the garage. Aaron2 explains that he wants to change what happened at the party because he wants to get the ex-boyfriend arrested so he can’t *potentially* harm Rachel in the future. Abe2 is hesitant to mess w/ the future, but in the end he agrees.

Aaron2 tells Abe2 about his earpiece strategy. Abe2 starts wearing one too.

Aaron2 goes to the basketball court & tells Will about Robert’s party, and tells him to bring his cousin (Rachel’s ex-bf). Aaron2 and Abe2 go to the party & take the bullets out of Rachel’s ex-bf’s gun. The ex-bf threatens Rachel but this time Aaron2 saves the day. The ex-bf is arrested as they planned.

But at this point we’re wondering what happened to Aaron.

Aaron2, on the voiceover, explains it. He found out that Abe had the failsafe by checking the storage records & noticing that Abe had 2 lockers. Aaron finds Abe’s failsafe & is upset. Aaron takes one of the time machines & puts it inside the failsafe, travels back in time, then Aaron2 immediately puts the smuggled time machine into his own secret location & turns it on. That provides Aaron2 a secret failsafe of his own to wipe the time slate clean (as a primer does for painting, as suggested by someone else on the primermovie.com site).

Aaron2 then drugs Aaron’s milk at night, which Aaron eats in the morning (daylight) and passes out, and Aaron2 puts Aaron in the attic. This lets Aaron2 take over Aaron’s life for a bit.

Here’s a part that I don’t understand. In the next scene, we see the Aaron2 drugging the milk scene again (at night), but this time you see an Aaron overpowering another Aaron at night. But then another Aaron enters the room & sees this, but he talks to the standing Aaron & agrees to leave, saying “see you” because the drugging was already done. There are 4 Aarons here; 1 Aaron is asleep waiting to have milk in the morning, another has been knocked out on the floor, another knocked him out, and another came through the door. I think Aaron2 was the last guy with the white shirt that walks out the door. I think Aaron found out that Aaron2 drugged him, so he went back to stop it? I dunno…

Aaron2 and Abe2 argue at the airport about where to go. They note that Abe and Aaron are about to get out of the closet/attic & start building their machines. Abe2 has been sabotaging the effort to stop any more Abe/Aarons. Aaron doesn’t want to do that; he just wants to leave. Aaron goes to another country & starts building his own machine.

The voiceover is Aaron2 talking to Aaron on the phone. I think Aaron2 is telling Aaron so he has an advantage over Abe2.

what happens to the relationship. None of them trust each other. They are egotistical and greedy. Eventually the main characters', Abe/Aaron, relationship deteriorates, and they go their separate ways.