In the 10th book of the popular series, rumors fly of Napoleon's planned invasion of England, and British naval commander Thomas Kydd is sent to liaise with American inventor, Robert Fulton, who has created "infernal machines" that can wreak mass destruction from a distance. Fulton believes that his inventions, namely the submarine and torpedo, will win the day for the power that possesses them, and Kydd must help him develop the devices. Despite his own scruples, believing that standing man-to-man is the only honorable way to fight, Kydd agrees to take part in the crucial testing of these weapons of mass destruction, which just may decide the fate of England.