Alvirah Meehan, the lottery winner turned amateur sleuth, recently "hitched" private detective Regan Reilly and their husbands are all guests on the Royal Mermaid's maiden voyage, the Santa Cruise. The cruise is Commodore Randolph Weed's gift to a select group of people who in the last year made the world a better place. What the Commodore doesn't know is that his ne'er-do-well nephew, Eric, has smuggled two escaping criminals on board.

The ship's passengers include a writers group, who are planning a mystery seminar dedicated to a Ghost of Honour - the late Left Hook Louie. But the hoped-for tranquility quickly vanished when a terrified mystery fan swears she has spotted the Ghost of Honour in the ship's chapel, and soon after - while a storm develops - an attempt is made on the life of a feeble passenger. Back in Miami, a TV reporter is turning the cruise into a public-relations nightmare.

As the Royal Mermaid sails on through troubled waters, Alvirah and Regan are uncovering clues that lead them to dangerous criminals.