Shortly before noon on June 4, 1944, the sonar operator on a destroyer prowling off the coast of West Africa heard a sharp, metallic ping. The sound could mean only one thing: the German U-boat that their hunter-killer group had long been tracking, U-505, was lurking somewhere in the darkness beneath them. The ensuing fight between exhausted hunter and venomous prey would make history when American sailors boarded an enemy warship at sea for the first time since the War of 1812.

That day's victory was the culmination of a tireless campaign against the Nazi submarine threat by "Tenth Fleet"--a mysterious unit possessing the oracular ability to predict the locations and movement of Hitler's U-boats. Run by Commander Kenneth Knowles, Tenth Fleet had guided Captain Dan Gallery to U-505 and to repay the favor Gallery was going to steal an Enigma machine for him. Now all they had to do was to make a U-boat, its crew, and its secrets vanish into thin air . . .

In this swashbuckling adventure story, bestselling historian Alexander Rose draws on long-classified encrypted documents and intercepted German transmissions to unravel, for the first time, the astounding tale of a daring heist cooked up by an owlish egghead and a glory-seeking buccaneer to score the richest prize on the high seas.