Sheldon's relationship with Stephen Hawking is threatened over a game of "Words with Friends," and Penny secretly enrolls in a class at the local college.

A young man with a brilliant memory is abducted and forced to remember the specifications for a new "smart gun" in a high tech research facility.

Damon goes with Elena and Bonnie to visit Whitmore College, where Professor Shane is taking over the Occult Studies classes formerly taught by Bonnie's grandmother. At a fraternity costume party, Damon takes advantage of the wild scene to give Elena a lesson in choosing a victim. Rebekah's attempt to buy Matt's forgiveness falls flat, but she is intrigued by unexpected news from Klaus. When Stefan questions Klaus about Connor's motives, Klaus reveals a long-ago encounter with a powerful group of vampire hunters, but it's Rebekah who delivers the information that stuns Stefan.

Demi Lovato and the Young Adults: Paige Thomas, Janelle Garcia, CeCe Frey and Willie Jones, L.A. Reid and The Over 25s: David Correy, Vino Alan, Tate Stevens, Jason Brock, Simon Cowell and the Groups: "Sister C", "Lyric145", "1432" and "Emblem3" and Britney Spears and the Teens: Arin Ray, Diamond White, Beatrice Miller and Carly Rose Sonenclar are up for the results as the judges have one last vote to pick which acts will form the Top 12!

George begins treating a cockatoo that keeps mysteriously ingesting chocolate. While George tries to manage the eccentric owner, Sabrina French, Doug sets his sights on the socialite granddaughter, Tinsley French. Dorothy begins a movie night but when only Yamamoto shows up the two make the most of it. Meanwhile, Angela and Dr. Rizzo have to call the cable guy when their favorite legal program "Law of the Jungle", is interrupted. Smitten with the cable guy's take-charge manner, Angela schemes to get him back ASAP.

Walden faces a dilemma, choose Rose who just moved in, or Zoey, who wants him back.

When an investigative reporter gets too close to the head of HR, her number comes up and Reese must get close to her without revealing that he is the mystery vigilante. Meanwhile, Fusco finds himself torn when Simmons tells him to help HR... or else.

The All Stars are tasked with recreating and updating a 70's disco style using Nine West shoes of their choosing as inspiration! Designer Rafe Totengco guest judges.

Vincent revives a 19-year old boy who was left for dead in a dumpster and rushes him to the E.R., where he remains in a coma. After Evan declares that the boy's x-rays reveal a history of bone fractures, Cat and Tess question the father, Zachary Holt, who worries that his son's ADHD and history of fighting and gambling might have gotten him mixed up with the wrong crowd. The detectives question Lois Whitworth, who owns the Westchester Polo Club where the boy worked. Lois is surprised to learn that her daughter, Clarissa has been dating this young man. Clarissa claims that she ended the relationship because he was involved in illegal activities, but Cat and Tess suspect that there's more to her story. Meanwhile, Silverfox and his Murifield agents track down Cat, and offer to tell her the truth about her mother in exchange for turning over Vincent, who they insist is a monster. Cat tells Vincent about her Silverfox encounter, and Vincent realizes that Cat might be afraid of him. JT wants them to flee, but Vincent refuses to leave Cat, instead offering to surrender to Silverfox in exchange for Cat's safety.

Charlie and Dee become romantically involved with two members of a wealthy family, which arouses jealousy in Mac, Dennis, and Frank.

Mike gets confused about the rules of being in a relationship; Deena must fight for her right to party.

Sherlock tries to determine who has been killing weak and terminal patients at a hospital, making it look like they died of natural causes. Meanwhile, Sherlock learns more about Joan's decision to walk away from her surgical career.

Kevin and Jenny discover Kristin Cavallari is in their baby group. Taco realizes he may actually have a girlfriend. Ruxin needs Rafi to take his son to swim class. Not a good idea.

Bob Woodruff

John C. Reilly, Casey Wilson, Cory Chisel

David Byrne & St. Vincent

Judy Greer, a Top Ten List presented by Joe Biden, Aerosmith

Jamie Lee Curtis, Maggie Elizabeth Jones, ZZ Ward

Lola has no friends or pets so she gets a law degree and defends Owen.

Alphonse goes home to Alaska to investigate his partner's death and repair a rift with his father.

Joel McHale, Wolfgang Puck

Gavin is hit hard by the death of his dog Chester and, understandably distracted, accidentally leaves out a document detailing staff wages, which Leighton promptly pins up on the noticeboard.

Jeremy Clarkson is this week's host while the panelists include Tony Law.

It's Alfie's birthday at the bar and Gemma ends up encouraging Billy to date another woman. Tom attempts to help Fran pull the man of her dreams. Inca overhears some information that has a really bad effect on her relationship with Jason.

Referee James Corden welcomes the most successful British Olympian of all time, Sir Chris Hoy. Fellow Olympian Rebecca Adlington and David Walliams also guest.

Stephen Fry looks into a jumble of things that start with the letter 'J'. With Jo Brand, John Sessions, Dara O Briain and Alan Davies.

Graham is joined on the show by Robbie Williams, Paul O'Grady and Darcey Bussell.

Megatron forces Optimus to make a difficult choice for the team.

Conclusion. More of Tron's history before the occupation is revealed, including how he got his scars.