Munch spreads his usual Christmas cheer. Russert, who misses detective work, joins Meldrick on an investigation into the murder of a material witness, when she discovers she knows something about the victim's case. Munch and Bolander investigate the death of a man in a Santa Claus suit and Munch spends the evening with whom they believe is the victim's son. Beau buys Christmas presents for the kids, although he still doesn't know where Beth and the kids are. Bayliss searches the station in search of a game of hearts.

Tim's cousin shoots a Turkish exchange student and his partnership with Pembleton may be in jeopardy when they both stand on opposite sides of the case. Lewis hires his grandmother to cook at the bar.

Gee is sent upstairs to see Barnfather and everyone speculates about the vacant Captain's position. Lewis and Kellerman are sent to Pennsylvania to extradite a woman back to Baltimore where she is a suspect in the murder of her husband. Munch tries to find a videotape in Brodie's pile. Later after reviewing the tape, they discover a key piece of evidence isn't contained on the tape. Munch wants the tape erased, but Brodie delivers the tape to court and that results in the outcome Munch feared. On the trip back from Harrisburg, Kellerman convinces Lewis that they have time to stop at Neptune's Castle and they lose the suspect, for a moment. Later they lose her again but find her at the house of her dead husband's mistress, delivering a hat. Much to everyone's surprise but not the viewers Gaffney is promoted to Captain over Gee. Captain Gaffney lays down the law.

Jake Rodzinski has trouble dealing with the verdict of the trial and takes justice into his own hands. Kellerman is back from a family wedding in Wisconsin picks up the case of the murder of Kenny Damon. Lewis is not allowed to know all the details of Kellerman's investigation, because of his past relationship with Rodzinski, their chief suspect. Bayliss is at odds with Pembleton over the disposition of a grilled cheese sandwich.

A man transporting 72 condoms filled with heroin bound for Luther Mahoney is found dead in hotel. The department takes this opportunity to set up ""Operation Get Luther."" The operation almost goes off as planned, except Luther Mahoney gets Lewis' gun and is holding it on him as Kellerman and Stivers enter. Frank and Tim agree to become partners again. Tim stops by to see his uncle. Munch takes a call from a convict who was looking to talk to Bolander. He has information on an old murder case that should be a done deal. That involves the digging up of section C of the parking lot at a racetrack. Munch discovers that the supposed victim is alive; however, he isn't that way for long.

Sheppard and Lewis investigate the death of a man who has a twin brother. Gharty talks about wanting to live his life; he and Ballard go to the hospital to investigate the death of a teenager. Bayliss has interest in Sheppard; later he seeks advice from Stivers, who tells him to get in line behind Lewis and Falsone. Lewis and Sheppard interview the remaining twin and his mother; she confirms his story and they try to point to the dead twin's girlfriend. Meanwhile the friend of the teenage victim in Ballard and Gharty's case confesses that his friend wasn't shot in Baltimore, but rather D.C.; he drove his friend back to Baltimore so their parent's wouldn't ""kill them"" for buying drugs in D.C. Gee hopes to get the case moved to D.C. Mike Giardello puts in for his FBI transfer, but the only openings they have in the area are for liaisons to local police departments. He interviews with Gaffney, who is so open to the idea, he can't wait to tell Gee. That's something Mike was going to wait f