The film opens in a California forest as a group of alien botanists collect vegetation samples. U.S. government agents appear and the aliens flee in their spaceship, leaving one of their own behind in their haste. The scene shifts to a suburban California home, where a boy named Elliott plays servant to his older brother, Michael, and his friends. As he fetches pizza, Elliott discovers the stranded alien, who promptly flees. Despite his family's disbelief, Elliott leaves Reese's Pieces candy in the forest to lure it into his bedroom. Before he goes to bed, Elliott notices the alien imitating his movements.