Tracing their ancestry to a small Dublin town while honeymooning in Ireland, newlyweds Regan and Jack Reilly learn disturbing information about their families, a discovery with which they are aided by Jack's colleagues at the Major Case Squad.

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...

When Regan Reilly and her husband Jack join his siblings at his parents' vacation home on Cape Cod, it turns out to be anything but a relaxing time.