A Ford Anglia is parked on a street. A teddy boy, using stolen keys, steals it before its owner, struggling commercial traveller John Cummings, leaves work. Cummings reports the theft to the police but confesses to his wife that the Anglia's basic insurance does not cover theft.

At work, Cummings' failing sales figures have been noted by Alec Berger, the new managing director, and he misses several appointments when he is forced to use public transport.

Cummings decides to use his skills as a salesman to trace the car thief. He questions Alfie Barnes, the elderly newspaper vendor who witnessed the theft, and learns that the Anglia was stolen by Tommy Towers, who frequents a local café. Cummings pays the establishment a visit but is merely mocked by Tommy and his fellow Teds. Meanwhile, Towers' employer, Lionel Meadows, confronts Alfie and kills his pet terrapins. Alfie dies of a heart attack and Cummings, gathering his courage, breaks into Meadows' garage. The Anglia is not there and Cummings is brutally beaten by Cliff, Meadows' right-hand man.

Inspector Thomas, the officer in charge of the case, berates Cummings for his stupidity, as his interference has nearly ruined an investigation into Meadows' activities. At work, Cummings is demoted to the storeroom, a position from which he resigns after hurling a box of cosmetics at the head of a rival salesman.

Jackie, girlfriend of Tommy Towers and Meadows' mistress, escapes to seek refuge at the Cummings' flat. She is followed by a psychotically angry Meadows, who starts an altercation then leaves, threatening dire vengeance. Anne Cummings begs her husband to abandon his quest, but he is adamant. He confronts Tommy on his own, but the boy is terrified of Meadows' reprisals. Cliff chases Tommy and as he and Jackie hide in their shabby bedsit; Cliff warns them both of Meadows' anger.

As the day wears on, Cummings sits in the café. The Cypriot proprietor sympathetically tells him that there is no shame in being afraid. Mackinnon, one of Meadows' gang, has been arrested and the Inspector coerces him to talk. Tommy and Jackie see Cummings walk towards the garage and call the police. The Anglia is the only car left in the establishment and Meadows and Cummings fight before the police arrive. Meadows is arrested, Tommy and Jackie flee on a motorcycle and a bloodied but triumphant Cummings drives the Anglia home to his waiting wife.