It is autumn, 1941, and a German U-boat commander and his crew set out on yet another hazardous patrol in the Battle of the Atlantic. Over the coming weeks they must brave the stormy waters of the Atlantic in their mission to seek out and destroy British supply ships. But the tide is beginning to turn against the Germans in the war for the North Atlantic. Their targets now travel in convoys, fiercely guarded by Royal Navy destroyers, and when contact is finally made the hunters rapidly become the hunted. As the U-boat is forced to hide beneath the surface of the sea a cat-and-mouse game...