WATU's tactics are tested to the limit in the final conflict for ONS 5, with over 50 Allied ships and their escorts facing off against 30 German U-Boats. In the end, it is the allies who win out and the remnant of the U-Boat fleet is left to try and limp back to its base at La Rochelle. As the Battle of the Atlantic reaches its crucial turning point, however, the work of the WATU is not yet over. Dönitz makes one last, desperate throw of the dice, unleashing an advanced torpedo to try and turn the tide back in favour of his remaining U-Boats. Roberts and Laidlaw must do everything in their power to counteract the new threat and recapture the seas in time for the impending Allied landings in Normandy.