Basically, there is this center where people are doing tests on monkeys, they are forcing them to stay awake, and watch nothing but violent images 24/7. So these animal rights people break in, and try to get them out. They are about to let them out when a doctor catches them and tells them that they are "infected" and are VERY dangerous, and contagious. They don't listen (of course
) and open one of the cages, letting the monkey out and that starts the spread of the "infection" which supposedly kills most of the people in the world, leaving only a few alive and normal, and the rest still "infected" trying to kill the ones left alive.
It sounds confusing and maybe dumb but it was intresting