International jewel thieves Rand, Tom Gordon, Countess Sonya, Boris and Rocco converge at the fashionable California Hotel to await the arrival of Lillian Vanderhoven, a former burlesque queen who is now a wealthy dowager and the owner of the priceless Kimberley King diamond. Valerie, Gordon's niece, is ignorant of her uncle's true vocation and consequently believes that he and Rand, whom she met earlier, are friends on vacation. When Mrs. Vanderhoven arrives, Wyndy, Rand's valet who is posing as an English nobleman, is with her, having become part of her entourage. Wyndy, bent on stealing the diamond, is dismayed to learn that Rand has promised Detective Norris, to whom he owes a favor, that the jewel will remain safely in Mrs. Vanderhoven's possession. At a dinner party that evening, Gordon steals the gem while dancing with Mrs. Vanderhoven. Rand, who has become fond of Valerie, determines to retrieve it without letting her discover that her uncle is a thief. Surprising Gordon in the act of packing his suitcase, Rand forces him at gunpoint to hand over the diamond in Valerie's presence, leading Valerie to think that Rand is the real thief. After depositing the gem with Norris, Rand leaves the hotel with Wyndy, convinced by his own generous act that there is honor among thieves.
Oh, What a Night!
A man is keeping a secret from his young niece: he's an international jewel thief.
