This mystery is adapted from a Graham Greene novel and begins as a British spy arranges a meeting with his son, whom he hasn't seen in four years. They are to meet in Venice, but unfortunately, the spy is unable to make the appointment. The boy then gets a mysterious call from his father breaking their date. Meanwhile, a compassionate hotel receptionist convinces her American lover to help the boy find his father. The boy friend investigates and discovers that the boy's father had found a fellow spy in trouble and was captured and drugged while trying help him. Both of the British spies are then placed on a boat and sent to Communist Europe where the police cannot catch them. Fortunately, the brave Yankee devises an ingenious plot to save them.