1941. We are in the midst of World War II. Great Britain, that fight alone against Nazi Germany, is on the verge of collapse: the German submarine blockade continues to deprive England of a vital part of its supplies. The Germans are working on a new submarine project, the Type XVIII, propelled by revolutionary HTP engine designed by Professor Helmut Walter.
To get more information on this secret project, Churchill sent in action in a German naval base in northern France, the Royal Marine Commandos. Their target is to penetrate the whole Kriegsmarine command and seize all the secret information.