Bob Bolles is an ex-Navy pilot who lives for drinking and lounging onboard his sailboat in the Caribbean. In need of cash, he allows himself to be talked into paying passengers, an American couple wanting to go to Mercator Island. The two are actually Vichy agents on a mission to obtain a device there and plan to kill Bolles as soon as they do not need him. When the woman falls in love with Bolles, she seeks the aid of Mr. Moto to make their escape. Mr. Moto, wanting the device as well, agrees to help.