German agents infiltrate an Iceland port used by the US Navy for anti-sub patrols protecting convoys. Their goal is to block the harbor and trap the patrols. The officers in charge must stop the plot before the subs are left unchecked.

American naval forces are using a port in Iceland as a base for anti-submarine patrols to protect North Atlantic convoys from German subs. The Germans 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.—[email protected]