Mediterranean, 1943. Lurking in the Dodecanese, an unknown terror has been ambushing British submarines. Lieutenant Peter Sinclair, R.N., Captain of H.M. Submarine Rugged and the youngest Commanding Officer with the famous 'Fighting Tenth' Submarine Flotilla, sets sail. His mission: to destroy the enemy. In the Turkish city of Istanbul the discovery of a murdered agent reveals a cryptic message, a message which, once deciphered, reveals the existence of an enemy fortress producing a lethal weapon. Behind it all is Sinclair's nemesis - a ruthless and deadly S.S. Kommandant prepared to commit mass murder. In a remote and hostile region, Sinclair, Commando Lieutenant Hank Jefferson, U.S. Navy and Able Seaman Bill Hawkins carry out a daring raid to destroy the plant. But with time fast running out will they succeed? And will they all make it out alive?