Alvirah Meehan, the lottery winner turned amateur sleuth, and her husband Willy, private detective Regan Reilly, her new husband Jack, and Regan's parents are all guests on the Royal Mermaid's maiden voyage, the Santa Cruise. The ship's passengers include members of the Oklahoma Readers and Writers group - who are planning a mystery seminar dedicated to a Ghost of Honour, the late Left Hook Louie - as well as assorted other charitable folk all planning on a restful post-Christmas vacation. What the guests don't know is that two escaping criminals have been smuggled on board. The hoped-for tranquility quickly vanishes 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 outside - an attempt is made on the life of a feeble passenger. As the Royal Mermaid sails on through troubled waters, Alvirah, Regan and Jack are uncovering clues that lead them to dangerous criminals.
At the start of the lighthearted fourth yuletide mystery from the bestselling mother-daughter Clarks (after 2004's The Christmas Thief), Randolph Weed, "self-styled commodore," launches his newly refurbished boat, the Royal Mermaid, from Miami with a "Santa Cruise" to raise money for charity and reward 400 "Do-Gooders of the Year." Meanwhile, Weed's greedy nephew, Eric Manchester, has made a secret $2 million deal with escaped felons Bull's-Eye Tony Pinto and Barron Highbridge to keep them hidden aboard the Royal Mermaid until it reaches Fishbowl Island, where they can make trouble out of federal jurisdiction. Fortunately, there are plenty of Do-Gooders to foil the bad guys, notably the mystery mavens of the Oklahoma Readers and Writers group and sleuthing philanthropist Alvirah Meehan. Full of mystery-lite cheer but lacking in style and substance, this collaboration is never quite buoyant enough to really deck the halls for fans of the Clarks' superior solo efforts.