Murder on the Leviathan by Boris Akunin
Investigating the bizarre murder of an English aristocrat whose children and servants were found dead nearby of apparent morphine overdoses, police commissioner Gauche follows clues on a luxury cruise ship, where he teams up with Erast Fandorin to identify a dangerous on-board killer. By the author of The Winter Queen. Reader’s Guide included. Reprint. 27,500 first printing.