Jenna annoys Liz with her wedding envy, Jack devises a plan to avoid disappointing his visiting mother and Tracy attempts to cheer up Kenneth.

Sheldon tries to nurse a sick Amy back to health, while Wolowitz prepares for an upcoming fishing trip with his father-in-law.

This is the first of the two-part series finale, and Team One faces a serial bomber who takes an entire city hostage. They are put to the ultimate test in this shocking conclusion, changing Team One forever.

When Stefan confronts Damon with a suspicion about Elena, Damon has no choice but to help Stefan investigate. Searching for answers, Damon and Stefan visit modern day New Orleans to see if they can find anyone who remembers the events of their last visit in 1942, including one of Damon's former flames, Charlotte. Elena, Caroline and Bonnie share a girls' night while the Salvatore brothers are out of town, and emotions run high when Elena delivers some shocking news. At Hayley's urging, Tyler confronts one of Klaus' hybrids, Kimberly, and the situation quickly escalates into violence. Finally, Damon is faced with a heartbreaking decision.

Results Night and Demi Lovato and CeCe Frey, L.A. Reid and Tate Stevens, Simon Cowell and the Groups: "Fifth Harmony" and "Emblem3" and Britney Spears and the Teens: Carly Rose Sonenclar and Diamond White are going to have to see if they did enough to escape a Double Elimination. Musical Guests: Melanie Amaro and Ke$ha.

The crew of the Colorado wait for a goodwill visit from their families, a visit that will soon turn into a nightmare as Marcus must consider the unthinkable once again. Meanwhile, the true reason for the nuclear devastation in Pakistan is revealed.

Alan helps Walden create a new identity so he can avoid women who are only interested in his money.

While Reagan secretly hangs out with her ex-sister-in-law, Connie, Chris and Scott compete for jobs against Scott's ex-father-in law. Meanwhile, Ava takes a fan and her family on an unusual "Hollywood" tour.

The new batch of interns find themselves involved in all the drama at Seattle Grace: Meredith asks Heather to go above and beyond to help fix Derek's hand; Cristina starts a healthy competition between Stephanie and Leah, which inadvertently leads to a medical emergency for Cristina's patient; Alex sees Jo in a new light as they work to save a baby's life, and April teaches Shane a valuable lesson during "lumps and bumps" duty.

When the office holiday party fizzles, Dwight throws a traditional Schrute German Christmas. Meanwhile, Darryl suspects that Jim has forgotten to include him in a new job opportunity in Philadelphia, and Pete teaches Erin about the film "Die Hard".

As New Directions regroups after Sectionals, Finn ponders his future with the club. Meanwhile, Rachel prepares for the NYADA Winter Showcase, and Kurt gets his shot at redemption with a second audition.

A Cuban defector comes up as the next Number and Reese and Finch try to pinpoint who might be after him. Meanwhile, Carter tangles with the Secret Service while HR tries to make amends with Elias and sends Fusco to negotiate.

The All Stars gather at NYC's Highline and are challenged to create a red carpet gown using only green, eco-friendly fabrics and materials. The legendary Diane Von Furstenberg guest judges.

JT suspects that Catherine is the trigger of Vincent's blackouts, so to disprove this theory, Vincent allows JT to inject him with endorphins and sedatives that force him into a fugue state. In flashback, Vincent recalls his time in Afghanistan when he received his first super soldier shot, and remembers who injected him with the DNA altering substance. He also recollects how the other soldiers experienced unpredictable side effects, including fugue states, and is relieved to know that Cat isn't causing his blackouts. Vincent shares his memory about Murifield with Cat, who experiences some recollections of her own. Then, as Cat and Tess investigate the attempted murder of a teen pop star, Evan suspects that Cat is deliberately protecting the vigilante who saved him in the subway.

Ron, Diane, and Leslie attend a wood working awards dinner, after one of Ron's handcrafted chairs is nominated, but the happy occasion is threatened by the arrival of Tammy II. Meanwhile, Jerry hosts a holiday party at his home with his wife, and some of his friends are shocked to find they were not invited.

After slipping into an unhealthy obsession with computer games, The Gang wrestles to define the difference between the real and the virtual worlds.

Michael brokers a deal selling an expensive piece of technology to a ruthless thief. But things become complicated when Sam is dragged in as part of a high stakes robbery. Meanwhile, Madeline goes to Barry to ask for a dangerous favor.

Vinny and Jionni resolve their differences; Mike acknowledges his past mistakes and attempts to make amends.

A national tragedy forces Olivia to return to work at the White House. Meanwhile, we learn more about the first few days of Fitz's presidency.

Sherlock uses his trademark deductive reasoning skills to find the killer of a college professor, Meanwhile, Watson gets a call from a former lover who needs her help.

Ruxin is worried that Sofia has soured on their marriage, the guys try to shake free of an undesirable acquaintance, and Jenny uses insider information to make a dirty trade.

Gov. Chris Christie

Andre takes advantage of Kevin after his colonoscopy, Pete suspects his Grandpa Duke is committing adultery, and the group enlists Rafi to settle a League dispute when no one trusts Ruxin to do it.

Ty Burrell, W. Kamau Bell, The Gaslight Anthem

Andy Serkis

Gary and Joel learn the meaning of school pride when a turf war erupts with prep school kids over their prized food mart.

Bill Murray, Vintage Trouble

Bill O'Reilly, Krysten Ritter, Paloma Faith

While celebrating Christmas together at Kove's house, the team is attacked by the evil Alaskan Santa Claus.

Denis Leary, Richie Sambora

Karl and Warwick's journey continues as they make their way to India. Laughing yoga and parts in a Bollywood film are trumped after Karl experiences his first holiday highlight.

David Mitchell guest-hosts the satirical quiz, with journalist and broadcaster Janet Street-Porter and comedian Susan Calman joining Ian Hislop and Paul Merton to take another sideways look at the week's news.

A familiar face is welcomed back into the fold as former Red John Bishop returns. He's joined by Olympic champion Victoria Pendleton and Comedian Sarah Millican.

Stephen is joined on the show by Brian Cox, Rhys Darby, Jason Manford and Alan Davies with this week's theme being justice.

Graham is joined on the show by Daniel Radcliffe, Jessica Ennis and Bruno Mars.