American naval forces are using a port in Iceland as a base for anti-submarine patrols to protect North Atlantic convoys from Nazi subs. The Nazis send undercover agents into the port in a scheme to blow up the entrance to the harbor and keep the patrols blocked in. The officers in charge of the patrols have to find the spies and stop them before they achieve their objective.

casts

Bruce Bennett

Virginia Field

John Beal

Larry Parks

Lloyd Bridges