Grissom, Warrick, and Nick investigate the case of man who apparently was murdered and pushed off a six story building. Grissom's involvement is cut short by renewed hearing problems. Catherine looks into the murder of man outside of his regular bar.
Jack forces Nina to help with a sting operation against her contact in the hopes that he can lead them to the bomb. Palmer and Mike try to gage Stanton's loyalty when they investigate the chopper crash. George has a final conversation with his son.
Charlie and Lisa learn about their daughter Allie's amazing powers while trapped in a perilous situation. Mary Crawford lays the groundwork to snatch the child for government research.
Nick takes the case of a 16 year old mom who wants to put her baby up for adoption, after her father ends up being arrested for the murder of the 16 year old's very ill mom. Brian Olsen (LuLu's Husband) ends up being accused of negligence.
Frasier and Niles bicker over who gets to host the family Christmas celebration. When it seems that Martin will have to work, they decide to bring Christmas to him, with disastrous results. Meanwhile, Roz finds herself attracted to a hunky shopping mall Santa.
Andy and Theo move out. Tony thinks about calling it a day with his ex-wife. Sipowicz and Clark Jr look into the threats made to Clark Sr. A distressed, schizophrenic young man keeps saying "she can't breathe".
Kelly travels to Europe for a series of interviews and appearances. She is upset when her bag is lost (apparently seized by security because of concerns over her gun-shaped pin), leaving her without any extra underwear. She first visits Germany, where she deals with several adoring fans and tries to fake her way through a radio interview conducted in German. Kelly then goes to England to perform ""Papa Don't Preach"" on Top of the Pops. Jack heads to North Carolina to film a guest spot for Dawson's Creek. Sharon is depressed about the fact that everyone is away at the same time. Ozzy tries to cheer her up by building a fire outside the beach house so that she can spend some time outside. The fire department gives him some advice on building a pit for the fire, but the ocean is not very cooperative. When the fire finally gets going, Ozzy gives Sharon a good laugh when he tries to catch a fish in the ocean--and ends up falling on his butt.
Paul tries to find perfect gifts for the family to make up for last year's Christmas fiasco. Kerry finds a stray dog during the holidays. Cate is overjoyed when she is asked to sing a solo at the church's midnight service, but fears that seeing her family there will make her nervous.
Misty has returned to Cerulean City to step in as the Cerulean Gym Leader. But as soon as she arrives, she hears a news report about the Pokémon Investigation Agency closing Gyms that fail to meet proper standards—and rumor says Cerulean City is their next stop! Unaware that three of her enemies are in town, Misty rushes to the Gym and finds an out-of-control Gyarados in the pool. Neither Nurse Joy nor her sister's fan club can control it, and she can't just stick it in its Poké Ball while it's still upset. It's Misty's duty as Gym Leader to solve the problem, except she's also had a Gyarados phobia ever since she was a baby! Misty puts on a water show costume and swims in the pool, hoping to stir Gyarados's memories of performing together back when it was a Magikarp. Instead, Gyarados turns the pool into a raging whirlpool, and Misty blacks out. As her Horsea rescues her, she dreams of Ash and Brock telling her she can do this on her own.
When Jackie's father is arrested for bribery, Kelso thinks she'll come running back to him. But when Hyde and Kelso get into a brawl over Jackie, Kelso accidentally shoots Hyde with a BB gun and all hell breaks lose. Donna and Eric argue over how Hyde should deal with Jackie's pain. Meanwhile, Fez realizes he has a crush on his boss at the DMV.
Cheryl and the kids are invited to a neighbor's annual Christmas party, but Jim, who is feuding with the neighbor, isn't invited.
Zim's Yuletide plan to overtake Earth by posing as Santa starts to backfire when he takes on characteristics of the Jolly Old Elf. Dib, meanwhile, tries to save the population from impending doom.
A business trip to France is at stake as Andy and Byron jockey for Jessica's favor, with Andy promising to care for her cat, which he loses.
Bosco is dismayed as he watches Cruz go to the extreme lengths of planting drugs, frightening children, and faking a dying declaration in their attempt to arrest the drug dealer who killed another dealer and then tried to to kill the 12 year old boy who witnessed the crime; Nancy tells Ty that she's ending her relationship with Hancock, and gives Ty the ammunition he needs to get out from under Hancock's thumb and back to duty at the 55, as well as getting Sully's suspension from duty lifted.
Robert gives Ray a great idea on what to get Debra for Christmas, but he isn't very happy when Ray takes all the credit for it.
Dil's first Christmas finds Santa Claus driven to quit the toy-giving business by Angelica, who's unhappy about her gift: a "dumb" reindeer doll. Elsewhere, the grown-ups get snowed in at a re-creation of a pioneer cabin designed by Stu.
The next generation comes into play, as the children of both Jacob Clarke and Jesse Keys become the focus of both a government investigation and alien interest.
Not willing to breach confidentiality Lily makes a sacrifice to keep a late night confession secret. Elsewhere Dr. Macy and D.A. Walcott are forced to work together to put a sexual predator behind bars…where he belongs.
In the Season Four finale, Tony and Carmela contemplate purchasing a shore house, but a voice from the past threatens the deal. While Uncle Junior breaks out the Hearty Burgundy, Little Paulie and Benny break in a new sound system on the Stugots. With Carmine apparently intent on putting the past behind him, Tony and Johnny Sack weigh their options, carefully.