September, 1944. Fresh from liberty on the island of Hawaii, Horatio Culpepper, Captain of the U.S.S. SEAVIPER - one of the Navy's diesel-electric submarines, receives an order from Vice Admiral Stallerman, along with top-secret information from President Roosevelt, to rescue a downed American airplane near Sumatra. The downed pilot, an American Navy airman, is rescued with two escaped prisoners-of-war (POW) from a nearby island. But the Japanese and Germans are also discovered to be on this island together, and the submarine's landing party needs to separate. They discover that the Germans have converted U-234, a mine laying U-Boat, into a long-range submarine. They also find that the Germans have transported a deadly cargo across the Pacific to deliver to the Japanese. Why then, is this cargo so important? Forced to return to the boat while the Captain stays behind, the Chief of the Boat, Chief Keenan, realizes that he must deal with unexpected changes in command. The Executive Officer, Roitman, suffers a head injury during a depth charge attack and is relieved of duty. His rival, another officer named Cutter, rises to command. A stuck torpedo, a flooded compartment, and structural damage to the boat from a Japanese destroyer all become life-threatening, and the boat's survival is in question. Under the direct order from the boat's Captain to maintain position and meet the landing party at a scheduled rendezvous time, Chief Keenan finds himself in a power struggle against Cutter, whose defiance of the Slipper's direct order threaten their survival. With only enough high-pressure air to ballast Seaviper to 100 feet, decreasing oxygen, and a Japanese destroyer in wait, will she be able to return to the and foil the enemy's plan before it's too late?