Society matron Mrs. Fanshaw Renwick entertains lavishly at her posh home. Living with her are her two daughters, Phillipa, a madcap eighteen-year-old, and her married sister Errica who is having an affair with Ralli, a designing South American. When Captain Chantry arrives with an impressive letter of introduction, Mrs. Renwick welcomes him while Phillipa falls in love with him. On the night of the masquerade party, Phillipa induces Chantry to take her to the party in disguise, because her mother will not permit her to attend. The captain, in reality a jewel thief, readily complies, believing it will provide him with the perfect opportunity to steal Mrs. Renwick's famous pearls. Chantry's scheme succeeds, and in the midst of the excitement over the missing pearls, Phillipa decides to substitute herself for her married sister at Errica's rendezvous with Ralli, in the hope of breaking up their affair. Errica begs Chantry to save Phillipa from Ralli's designs; and the thief, who has ...