On November 22, 1963, Mister and Misses St. Cloud hear about the tragic assassination of the President of the United States John Fitzgerald Kennedy. Consumed with paranoia and believing that WWIII is now inevitable, they take their small children Tina, Pam and Scotty and hide with them in their fallout shelter, never to leave it again. By 1993, the parents had died but their three grownup manchildren still live in the nuclear bomb shelter alone without any human contact. They've developed their own rules and rituals based on their fading memories of the life above, their old records that still work and whatever they catch on TV, when some station's signal reaches them now and then for a few moments. Most of their day is spent in play sessions, in which they act out various common activities like going to school, eating out or staging musical numbers. They love to dance, sing and on occasion wrestle. Sometimes they even play their parents and reenact the parents' speeches to them. At one point, Tina and Scotty even pretend to be boyfriend and girlfriend but in a quite innocent manner. They play many other bizarre games that only make sense to them and tell each other stories that are amalgams of things they heard about like the Bible, Superman or the Pledge of Allegiance. Scotty even has a make-believe superhero alter ego - Supercar. The movie uses vignettes to tell the story but there's also a thin central plot that revolves around the fact that Mom and Dad gave the only key to the vault with food to Pam. The story is based on a stage play