Murder on the Leviathan (Erast Fandorin Series #2)

In 1878 Paris, Police Commissioner "Papa" Gauche must solve a brutal murder. Lord Littleby has been found at home with his head bashed in, surrounded by the bodies of seven servants and two children who all seem to have died from morphine poisoning. The only clue Gauche has to go on is a gold key in the shape of a whale. This key gains entrance to a luxury liner, the Leviathan, whose maiden voyage is to India. Gauche embarks, and finds among the passengers - all highly suspicious - Erast Fandorin, now a diplomat bound for a posting in Japan, but previously a crack inspector in the Moscow Police Department. When Fandorin discovers that a murderer is on board, he joins forces with Gauche to deduce the awful truth.