No Honeymoon for Death — Mary Kruger

Newlyweds Brooke and Matt Devlin are ensconced in a suite deluxe aboard the S.S. New York, sailing toward an idyllic month in England when fellow passenger J.P. Morgan asks the crime-solving duo to investigate the disappearance of another prominent financier. But the Devlins' search is complicated by the ship's detective, whose credentials are less than sterling, and by an actor who thinks he's Sherlock Holmes. With a full register of high-society suspects, Brooke and Matt must sort out a tangled web of perplexing clues and misleading motives before they can force a devilishly clever killer to pay the full fare for murder.