A valuable painting belonging to Duchess Blanca (Alida Valli) is stolen at night from her castle in Spain by one of her houseguests, Jimmy Bourne (Rex Harrison), who replaces the original work with a duplicate.

Eve wants to go straight, but Victor blackmails her and Jim, demanding that they steal a renowned painting (The Second of May 1808) by Francisco de Goya from the Prado Museum in Madrid.

An exact copy of the painting is created by artist Jean Marie Calbert (Joseph Wiseman), and a switch is planned to take place during the farewell bullfight of a famous matador, Cayetano (Virgílio Teixeira), whom the duchess intends to wed. During the bullfight, Victor secretly shoots Cayetano in order to create a diversion that will assist the art theft.

News of the matador's death spreads quickly across the city and distracts the guards at the Prado Museum, allowing Jim and Jean to begin switching the two large paintings.

Using the stolen Goya painting as a bargaining chip, Jim negotiates with the authorities, and he secures freedom for Jean and a reduced prison sentence for himself.