Two distinctly different couples—young British pair Steve and Michelle, and a sophisticated, predatory French couple, Christophe and Adrienne—arrive at the same London apartment due to a double booking. Enticed to share the space for the night by a suspicious letting agent, a night of heavy drinking, drugs, and group sexual experiences quickly turns deadly. As morning comes, the apartment becomes a inescapable trap, devolving into a violent struggle for survival controlled by sinister, hidden puppet masters.