Christmas is closing in, but the holiday is shaping up to be anything but merry. While out Christmas caroling, Shawn and Gus discover the dead body of their old neighbor, Mr. Fuller. Though it appears to be suicide, Shawn conjectures murder. The police ultimately agree with Shawn, but all evidence points to Gus' father as the killer. Shawn and Gus set out to prove his innocence.
Since Lassiter's recent separation from his wife has left him alone, Juliet invites him over to meet her family and share in some Scottish Christmas celebrations.