I was walking around the video store on Sunday when I noticed this film on DVD for the first time. I hadn't heard of it, but apparently it won an award at Sundance last year, so I knew that it couldn't be total crap. The box described some sort of time-travel puzzle movie, one that would be discussed, or at least pondered, for some time afterward. I rented it and watched it. And my mind was blown.
Two engineers begin building this machine in their spare time, and when they begin to discover its capabilties, they're seeing dollar signs. Then one of them discovers that it is capable of sending an object back and forth through time along a parabolic curve. But when they try to send some things forward or backward, the items always come back to where they started (the present) - except that the objects have experienced hundreds of cycles of forward and backward time travel within their own context, thus they have aged. So they figure that if they sent a person through a machine, that person could break the cycle whenever they wanted to - start in the present, exit in the past.
That's when things get weird. The plan starts out simple enough: find a stock that's jumped in price in one day, go back to that morning, buy a bunch of that stock on margin, reap the benefits. Then things get complicated, and I can't tell you any more about it without giving anything away. All I can say is that after watching it four times, I still have a hard time keeping tracking of everything in the final third of the film.
Fortunately, there is help. Don't click the next link unless you've either seen the movie or want to, because it has the whole story plotted out in great detail. http://neuwanstein.freeweb.hu/primer_timeline.html
Rent or buy this movie if you like intriguing stories that have to be figured out.