Addis, Hugh Dark Voyage.

This fair-to-middlin' murder mystery is set aboard an unnamed ocean liner during the final portion (Honolulu to San Francisco) of a voyage which had begun at Marseille with a run through the Mediterranean and Suez Canal into the Indian Ocean and then across the Pacific. It was certainly written during World War 2 and, perhaps to capitalize on current events, the author makes a weak stab at wartime references. Indeed, when the ship suddenly stops mid-ocean in order to recover a large steamer trunk that had been tossed overboard in the night (it has a body in it), panicky passengers assume that they've been torpedoed. Later, as news spreads of first one, than another shipboard murder, those same passengers fuel a rumor that "a Nazzy spy had a hand in this." That's about as convincing as it gets, however, since the liner had evidently sailed all the way from Marseille with lights ablaze and no real thought to the World War. It can only be surmised that the action is meant to be taking place sometime during the early days of the war, and certainly well before the Japanese attack on Pearl Harbor. If Addis' attempt at wartime "atmosphere" falls short, so does his plot which, in addition to the two shipboard murders, includes an insurance scam, blackmail and landside murders as well.