A series of murders in San Francisco bearing the tell-tale signs of the infamous Zodiac Killer have the BAU wondering if the notorious serial killer has returned. Meanwhile, Reid ponders if he should be doing more with his genius abilities.
Leonard is forced to face some insecurities when his case leads him to consider right and wrong. Meanwhile, Sandra takes on Seth, who files charges against a comic.
Nick and Hank investigate a series of strange home invasions. Monroe has a Christmas surprise for Rosalee.
The SWAT team looks for an escaped convict who is planning to kill Tan and the law enforcement team who helped put him in prison several years ago. Then, Chris arrests a young man who is given a free pass.