A convoy of 37 merchant ships is ploughing through icy, submarine-infested North Atlantic seas during the most critical days of World War II, when the German submarines had the upper hand and Allied shipping was suffering heavy losses. In charge is Commander George Krause, an untested veteran of the US Navy. Hounded by a wolf pack of German U-boats, he faces 48 hours of desperate peril trapped the bridge of the ship. Exhausted beyond measure, he must make countless and terrible decisions as he leads his small fighting force against the relentless U-boats.