Marine architect Hannah Bryson has landed the assignment of a lifetime. The U.S. maritime museum has just acquired the former pride of the Soviet fleet, the legendary nuclear attack sub Silent Thunder, for public exhibition. It’s Hannah’s job to inspect every inch of the decommissioned vessel and make sure it’s safe for the thousands of expected visitors. Enlisting the aid of her brother, Connor, they delve into its long and lethal history.

Then, on a routine check, Connor discovers a cryptic message behind one of the ship’s panels. Before he can figure out what it means, there’s a deadly assault on Silent Thunder. Now, although the U.S. government warns her against it, Hannah will stop at nothing to unravel the truth about Silent Thunder. Even if it means coming face to face with the ruthless mastermind behind the plot—and joining forces with a mysterious and seductive mercenary who is willing to kill to make sure the secrets about Silent Thunder stay silent. . . .