September 1907. George Dillman sets sail from Liverpool to New York on the Lusitania's maiden voyage. Posing as a passenger, Dillman is in fact an undercover detective hired by the Cunard Line to keep an eye out for petty crimes. But after some uneventful days aboard, the ship's blueprints are stolen and then a body is found. As Dillman works to get to the bottom of the crimes, he makes an unusual friend, first-class passenger Genevieve Masefield, and the two uncover secrets aboard the ship that prove explosive.