Christmas with the Gusters is ruined when Gus' parents' neighbor is killed, a clue leads Lassiter to look at Mr. Guster more closely. Evidence leads the police into arresting Gus' mother too, and Shawn and Gus vow to get them out of jail.

Shawn and Gus investigate a department store Santa who they suspect is up to no good. Meanwhile, Gus' sister flies in for Christmas.

Gus' nightmares start to feel like reality when he and Shawn work to solve an unlikely case for the SBPD.