Off the coast of Louisiana lies a Nazi submarine. Dave Robicheaux is tasked with locating its exact position on the seabed so it can be raised. Hippo Bimstine wants to turn the submarine into a casino as a tourist attraction on the banks of the Mississippi. Dave is not particularly eager for the job, but he needs the money to help his friend Batist, who has been arrested on suspicion of murder. Robicheaux quickly realizes that he is dealing not only with his client, who turns out to be a shady businessman, but also with a dangerous psychopath who wants to use the submarine for his own purposes. This individual will stop at nothing, not even to destroy Dave and his family. Their lives spiral completely out of control...