When a series of backyard pool homicides are reported in California, the BAU team searches for an UnSub with a puzzling past.
The team investigates the murder of someone from Booth and Brennan’s past. Meanwhile, Aubrey faces a moral dilemma of his own when he discovers his dad is back in the picture.
A man dressed as Santa robs a bank and gets lost in a Santa flash mob, Sharon's children come to town for the holidays and Buzz starts training as a back-up police officer.
Polly is nervous about applying for a promotion; Max and Elaine try to make sure that Natalie and Polly are living up to their full potential.