American adventurer, living in Tangiers, is persuaded by his two half-brothers to help pirate a million-dollar cash shipment belonging to their father who has browbeaten the sons until they are eager for revenge.

In this caper comedy, Duffy (James Coburn) is a shaggy bohemian living in Tangiers who is approached for a less-than-legal business proposition by two half-brothers, carefree Stephane Calvert (James Fox) and stuffy businessman Antony Calvert (John Alderton). Though Stephane and Antony had different mothers, they share the same father, and they both hate him; Charles Calvert (James Mason) is a mean-spirited multi-millionaire who shows his sons little affection and isn't very interested in cutting them in for the family fortune. Charles plans to transport several million dollars in banknotes by ship from Tangiers to Marseilles, and the brothers want Duffy to help them liberate the money from the ship. While the Calvert Brothers are persuasive, Stephane's beautiful girlfriend Segolene (Suzannah York) is even more so, and Duffy finds that he not only wants to steal the cash from Charles, but the girl away from Stephane. DUFFY was scripted by Donald Cammell, who gained a cult reputation for his first directorial effort, the Mick Jagger vehicle PERFORMANCE.