On a NUMA mission to the Black Sea to locate the wreck of a lost Ottoman Empire ship, Dirk Pitt and his friend Al Giordino respond to an urgent Mayday from a nearby freighter. But by the time they reach the area there's no one left alive. As they investigate the fate of the lost ship, they're plunged deep into an extraordinary series of discoveries. And when connections emerge between a desperate attempt in 1917 to preserve the wealth and power of the Romanov empire, a Cold War bomber lost with a deadly cargo, modern-day nuclear smugglers and a brilliant engineer developing cutting-edge drone technology, Pitt is faced with the most dangerous challenge of his career.