In Venice, Gaston Monescu (Herbert Marshall), a master thief masquerading as a baron, meets Lily (Miriam Hopkins), a beautiful thief and pickpocket also pretending to be of the nobility, and the two fall in love and decide to team up. They leave Venice for Paris, and go to work for the famous perfume manufacturer Madame Mariette Colet (Kay Francis), with the intention of stealing a great sum of money from her safe, which Monescu, as her secretary, arranges to be diverted there. In the course of things, Colet begins to flirt with Monescu, and he begins to have feelings for her.
Unfortunately, the plan develops a hitch when François Filiba (Edward Everett Horton), one of Colet's suitors, sees Monescu at a garden party. He is unable to remember where he knows him from, but when another of Colet's suitors, The Major (Charles Ruggles), tells Filiba that he once mistook Monescu for a doctor, Filiba suddenly remembers that he knows Monescu from Venice, where the thief robbed him, pretending to be a doctor. Monescu and Lily plan an immediate getaway that night, after they take all the money in the safe.
Colet prepares to leave for a dinner party given by the Major, but cannot decide whether to go or to stay and have sex with Monescu. Eventually she goes, but not before Lily catches on that Monescu has fallen for her rival, and wants to back out of the plan – so she robs the safe herself after confronting her partner. At the Major's, Filiba tells Colet about Monescu, but she refuses to believe it's true. She returns home and suggestively probes Monescu, who admits that the safe has been cleaned out, but claims that he himself took the cash. He also tells her that the manager of her business, Adolph J. Giron (C. Aubrey Smith), who has been suspicious of Monescu all along, has stolen millions of dollars from the firm over the years.
Lily then confronts Colet and Monescu, reporting that it was she who stole the money from the safe. An argument ensues, in which, eventually, Colet allows the two thieves to leave together. As a parting shot, Monescu steals a necklace from Colet that Lily had her eye on, and, in turn, Lily steals it from him, displaying it to him as the taxi takes them away, hugging each other.