I'll start off with some examples. Castaway - A really tanned, mildly insane man who lives alone on an island with a volley ball suddenly decides to leave one day after some garbage washes ashore. Close Encounters of the Third Kind - A man is obsessed with a mountain for no apparent reason decides to risk his life to sneak into a military base. Predator - Some army buddies trip acid and run around in a jungle hallucinating with guns.