Starting off as a prison drama and segueing into an espionage thriller, this film follows two escaped convicts who take over an island lighthouse being used by Nazi spies just after Pearl Harbor. Champ Larkin and his cellmate Jimbo break out of ¿The Rock¿ and make their way to a nearby offshore lighthouse station while avoiding the patrol boats. Forcing their way into the station, the escaped prisoners take captives as they plan the rest of their escape. But their scheme is complicated by a secret Nazi spy awaiting the arrival of German agents who are charged with an important mission: the destruction of San Francisco. Among the Nazis is a slim and youthful John Banner, two decades prior to playing cuddly Sergeant Schultz in TV's Hogan's Heroes.