It's NOT safe to go back in the water... After a promise gone horribly wrong, Gideon Black has sworn off doing favors for people. But when the mysterious Lady Tethys offers him a house—a home of his own for the first time in his life—in exchange for retrieving an artifact, he agrees. Unfortunately, the artifact is at the bottom of the Atlantic Ocean with a ship that went down four hundred years ago. To get to the wreck, Tethys arranges passage for Gideon and his friends with Captain Alex Walsh. But when they board the ship, they find that the crew not only know about and distrust Others, but are armed with cold iron weapons, one of the few things that can kill a Fae. And the captain is looking for any excuse to use them. Then they reach the dive site, and things go from bad to worse when the ship is attacked by something far more dangerous than humans with cold iron.