George, Tim Roth and Ann Naomi Watts Farber, their son Devon Gearhart Georgie, and their dog Lucky arrive at their lake house as their neighbor Fred Boyd Gaines drops by with two young men, Paul Michael Pitt and Peter Brady Corbet to help put the boat in the water, though Fred's behavior is off from the start.
While Ann is cooking, Peter visits and asks to borrow eggs. She gives him the eggs, he leaves, but drops them, then returns to apologize and asks for more. She gives him four more eggs and he leaves, but Lucky jumps on him, breaking the eggs. To Ann's frustration, Paul implores her to test one of his golf clubs outside, and Peter requests more eggs. George arrives and tries to oust them, ultimately slapping Paul. In retaliation, Peter bashes George's knee. The two men then take the family hostage.
Paul guides Ann on a game of Hot and Cold to find Lucky, whom he had killed with the golf club. When their neighbors, the Thompsons, visit, Ann claims Paul and Peter are simply friends of theirs. After returning home, the Farbers are forced to participate in a number of sadistic games in order to stay alive, during which they put Georgie's head in a pillowcase and ask Ann to strip naked. Georgie is hurt by Paul until he complies. When released from the pillowcase, Georgie escapes and goes to Fred's house, where he discovers bloody corpses.
Meanwhile, Paul ties Ann up before going out to search for Georgie, leaving Peter to watch over the Farbers. Ann asks why they do not directly kill them, and Peter answers that they should not forget the fun of the games. When Peter goes to the kitchen to get eggs, Ann jumps to George but George fails to free her before Peter comes back, and Peter beats her and breaks the eggs again. Ann begs Peter to let them go, but he refuses. Georgie finds a shotgun in Fred's house and Paul tells him to go ahead and shoot him with it, but the gun fails to go off, revealing the gun to be empty. Paul returns him to the living room, and gives the shotgun to Peter, and reveals the two missing shotgun shells.
The men play a new game, saying whoever gets counted out will be shot. While Paul is in the kitchen getting something to eat, Georgie panics and runs, which results in Peter shooting and killing him. Paul berates Peter for being trigger-happy, and the two men decide to briefly leave. George and Ann are grief-stricken over their loss, but they eventually resolve to survive. Ann is able to free herself and flee the house while George desperately tries to make a 911 call on the malfunctioning phone. Ann fails to find help, only to be re-captured by Peter and Paul, who bring her back to the house.
The next level of games begin with Peter stabbing George. They tell Ann to say a prayer before making a choice for her husband; a painful and prolonged death with the "little" knife, or a quick and brutal death with the "big" shotgun. While Paul is talking, Ann seizes the shotgun on the table in front of her and kills Peter. An enraged Paul grabs the shotgun and starts looking for the television remote. Upon finding it, he rewinds the last occurrences back to a moment before Ann grabs the shotgun, breaking the fourth wall. On the "do over", Paul snatches the shotgun away before she can grab it and admonishes her, saying she is not allowed to break the rules.
Peter and Paul kill George and take Ann, bound and gagged, out onto the family's boat. Ann tries to free herself but is caught by Paul and Peter. Paul nonchalantly pushes her into the water to drown. They knock on the Thompsons' house and request some eggs. Paul glances at the camera with a smirk.
