Movie Spoilers

Warning! If you don't want to know the endings or surprise plot twists to hundreds of movies, go no further! Turn back now!

12 Monkeys (1996)

The Army of the 12 Monkeys is a group of hippy environmentalists. They have nothing to do with the outbreak of the plague. Nonetheless, in researching the Army of the 12 Monkeys he has been very close to the actual source of the plague. When this is realized, he attempts to stop the outbreak by attempting to kill the bad guy but a cop kills Cole before he can do it. A young Cole witnesses the endgame and thus, we realize that the nightmares Cole has experienced since childhood are in fact memories of watching his own death. Oh, and yeah, Cole really is time traveler.

— Thanks to Dave Hall!