Nine years after the apparent suicide of Ferdy Villiers, the entire Villiers family reunites for Christmas. However, not everyone is imbued with the Christmas spirit, and the already tense atmosphere disintegrates quickly when it becomes clear that someone in the household is all too aware that certain family members have dark secrets to hide. Meanwhile, as Barnaby prepares to host his in-laws for the festive season, he's almost relieved to be called out to an incident at the Villiers estate.

DCI Barnaby and Sgt. Scott enter the world of horse racing when the trainer of a thoroughbred racehorse is brutally murdered. Investigating the four member syndicate that owns the racehorse in question, the detectives must unravel hidden secrets at the aristocratic Bantling Hall to uncover the killer.