The final days of the First World War, and the menacing bulk of the German battle cruiser Goeben lurks in the Golden Horn at Constantinople. It is vital that she is destroyed, or at least immobilized, and the favoured method is to send an E-class submarine in through the Dardanelles to the sea of Marmara. However, it is two full years since an Allied submarine has passed through the Dardanelles successfully - the narrow straits are now littered with minefields and nets, and are continually patrolled by gunboats. To send a submarine through now seems suicidal, but the alternative of sparing the Goeben is equally unthinkable. Aided by a Marine explosives expert and a taciturn intelligence specialist, Nick Everard is on board and in control, ready to run the gauntlet in his most dangerous mission yet.