Eli Yanakakis is the 9-year-old son of billionaire Rex Yanakakis, a man obsessed with the possibility of nuclear war. When a nuclear bomb falls on the United States, Rex brings his family into a large, furnished fallout shelter. Rex accidentally leaves behind his son Eddy, who is Eli's twin. Eli enters the compound with his parents, his older sister, Lexie, and his younger sister, Therese.
Six years later, Eli wonders if his brother may have somehow survived the fallout outside the family compound. Life in the compound is getting more difficult. 3 children have been born while the family is in the compound, but they are for a sinister purpose. As food is running out, and as Eli finds out more about the compounds dark secrets, Eli decides that he will do anything to get his family out.