An Unseaworthy Mission — Judith Campbell

No. 9 in the Olympia Brown Mysteries: Olympia is offered free room and board on a small cruise ship in exchange for being a guest lecturer, but the dream-come-true turns into a nightmare when she learns an elegant and persuasive male passenger is targeting wealthy, single, gullible ladies for personal and heartbreaking gain. Olympia realizes that despite cruise companies' best efforts, they can't always keep their guests safe and happy, because for some of life's miscreants a ship is a self-contained hunting ground where the unsuspecting prey are like fish in a barrel. Luckily for all, Olympia makes it her mission once again to set things right.