At secret naval maneuvers just before D-Day, American Colonel Hugh Kelso disappears in the English Channel. Dead or alive, within a few days the currents would wash him ashore on the German-occupied island of Jersey. The Allied High Command is in panic: Kelso knows the time and place of the invasion. He must be saved - or be silent forever... A British professor, disguised as a Nazi officer, and his companion, a young girl, a native of Jersey, disguised as his mistress, go in search of Kelso on an island carefully guarded by the Nazis. They must win the deadly game... or die.