Temporarily forsaking the Cunard Line to work as private detectives aboard the Minnesota, a combination freighter and passenger ship owned by the Great Northern Steamship Company, George Porter Dillman and Genevieve Masefield are eagerly anticipating the prospect of a cruise bound for the Far East. Once aboard, the two begin to establish separate social circles in order to keep an eye on as many passengers and crew as possible. As the ship gets under way, it's smooth sailing, and George and Genevieve are hoping that perhaps this will be their first uneventful cruise. Unfortunately, their luck turns quickly as a fiery Catholic missionary is murdered in what proves to be the first in a series of crimes that will stretch them to their limit. Dillman and Genevieve have to use all their skills to combat danger on more then one front and to prevent an otherwise idyllic (and romantic) trip from becoming a terrifying nightmare.