A woman sitting in a Parisian café reads a letter telling her to take the train to Venice, pick a man of the sender's height and build, and chat him up. She's being watched: Scotland Yard and a mobster with a crew of Russian thugs are looking for a man she knows. On the train, she talks to an American, Frank, suggests they have dinner, and, once in Venice, invites him to her hotel. The bait is set: the Russians think Frank is the man they want: Alexander Pearce, who stole billions from the mobster. Scotland Yard realizes Frank is a just a tourist, but by now he's in danger, smitten by the mystery woman, and in their way. Can the Yard keep Frank from death and still catch Pearce?