In this 4th novel in the series, Tom is asked to help save the crew of a sunken nuclear submarine, and then to recover the actual sub before it can be claimed as salvage and stripped of its top secrets by a foreign power. His successful efforts lead him to being requested to undertake a monumental task: locating and recovering the more than half-dozen "lost" nuclear submarines sitting on the bottom of several of the Earth's oceans. More than that, he must also find their nuclear-tipped torpedoes and reactors, some of which are no longer with their hulls, and recover them safely as well. With nothing available from his own company, it looks hopeless until the U.S. Navy loans him a holdover from the Cold War, a gigantic submarine carrier capable of holding and launching several attack class subs. He refits it for the mission, trains a half-Enterprises and half Navy crew, and sets out only to discover that saboteurs, spies, possible terrorists and even foreign governments are out to see him fail. But the ultimate danger comes later when they discover more than anyone could have ever believed