 The successful, honest and methodic lawyer James Manning works in London and is living in the country with his beloved wife Anne. Anne decides to have a party at their home, and the husband of their housemaid Maggie (Linda Bassett) is hit by a car at the same time nearby her house and Maggie witnesses a Land Rover. James associates the scratch on the car of his acquaintance Bill Bule with the accident, and forces him to confess and promise to go to the police on the next morning. When he arrives home, Anne tells him that she was driving the car; further, Bill is his lover. James changes his opinion and decides to support the lie, while a persistent detective is investigating the case and the list of guests.