While fifteen children at a summer camp are enjoying their carefree vacation together, they come across a small cave near the beach. Inside its caverns, the group discovers a mysterious room where they encounter a strange man who introduces himself as Kokopelli. He invites the children to play a game that requires them to take turns controlling a robot to defend Earth against aliens. Assuming it is merely an interesting computer game, all but one of the children sign a contract agreeing to participate. Later that day, the giant robot appears in person, and the children are teleported into its cockpit. There, they find Kokopelli, who pilots the machine in a battle against a similar robotic creature that has appeared nearby. After winning the fight, Kokopelli attempts to apologize, but he is interrupted as the children are teleported back to the ground amidst the carnage. As the bewilderment following the fight subsides, the robot suddenly vanishes, leaving the children scared and confused. Although the activity seemed like a harmless game at first, the children never anticipated the stakes involved or how their pasts would intertwine with their decisions going forward.