His dog. His computer. The tunnels under New York City.

That's all Joe Tesla's agoraphobia has left him with—the inside world, the dark world—and now the black depths of the sea.

In the latest book in this award-winning thriller series, Joe Tesla seeks to expand his world beneath. He buys a personal submarine to join an underwater scavenger hunt. The competition turns deadly when a mystery sub targets Joe. His search for answers drives him and his service dog out to sea where he alone might find answers in time to save the city he loves from annihilation.

But can a man trapped inside by his own fears save the larger world above?