The film opens on a seemingly happy family: George Farber, portrayed by Tim Roth, his wife Ann, played by Naomi Watts, their son Georgie, and their beloved dog as they arrive at their serene lake house. Nearby, their neighbor Fred is seen socializing with two young men, Peter and Paul, who, while friendly at first, quickly unveil their dark intentions. As they visit to borrow some eggs, Ann is busy in the kitchen while George and Georgie are outside near the lake, preparing their boat. However, this friendly interaction takes a sinister turn when the eggs they return are found broken.
Ann's frustration grows as the two return again demanding more eggs, leading to a violent altercation in which Peter shatters George's leg with a golf club, which escalates into a terrifying hostage situation for the family. Ann's attempt to call for help is thwarted when she realizes their cellphone is damaged beyond use, inadvertently destroyed by Peter earlier.
As their nightmare unfolds, Paul demands that Ann accompany him on a search for their dog, which he has brutally killed. When other neighbors arrive, Ann manages to deceive them, portraying her captors as friends until they leave, tightening the grip of terror around her family. The captors force the Farbers to partake in cruel and twisted games to determine their fates. During these unsettling games, Paul often mocks Peter, creating a disturbing dynamic between the two.
A panic-stricken Georgie attempts a brave escape only to be thwarted when he tries to use a shotgun against Paul, which tragically fails to fire. The oppressive tension heightens when Paul and Peter engage in a deadly counting-out game, leading to the heartbreaking death of young Georgie, shot by Peter in a moment of panic. This horrifying act leaves George and Ann devastated yet fueled with a lingering will to survive.
Determined to find a way out, Ann makes a desperate attempt to flee, but is soon recaptured by the sadistic men. After brutally stabbing George, the situation escalates as Paul offers Ann a horrific choice: a prolonged suffering for her husband or an instant death with the shotgun. In a moment of defiance, Ann seizes the opportunity to grab the shotgun, killing Peter in the process. This act of rebellion enrages Paul, who disregards the events that just unfolded, literally rewinding time to before Ann's act of defiance, breaking the fourth wall in a chilling twist.
On this new 'do-over' of events, Paul swiftly regains control, disarming Ann and reminding her of the so-called rules they are bound to. The dark cycle culminates as they brutally murder George and take Ann, now bound and gagged, onto their boat the following morning. Tragically, they throw her into the lake to drown while smugly adhering to their twisted bets. This shocking conclusion leads them back to their neighbors, where they casually request more eggs, reigniting their gruesome cycle of violence.
