When you're living underwater and also working as a spy for your city, things can get really dangerous. Truman McClusky has been out of the intelligence business for years, working the kelp farms and helping his city of Trieste flourish on the shallow continental shelf just off the coast of Florida. Until his former partner shows up, that is, steals a piece of valuable new technology and makes a mad dash into the Atlantic. Before he knows it, Mac ends up back in the game, chasing the spy to not only recapture the tech, but to kill his former friend. But when he learns the grim truth behind the theft, it sends his stable life into turmoil and plunges him into an even deadlier mission: evade the submarines of hostile foreign powers, escape assassins, and forge through the world's oceans at breakneck pace on a daring quest to survive, with more lethal secrets than he thought possible in his pocket. The future of the city depends on McClusky ... if he can make it back home.