House takes on a case of a patient with two different personalities as a result of having the left and right part of the brain operating independently.

The KTs race to return a stash of stolen campus goods, hoping not to get caught by security. Elsewhere, Casey sneaks Max into a faculty party so he can meet a visiting professor that needs an intern, and Ashleigh considers taking her relationship with Fisher public.

In a flashback to the 80s, 17-year-old Lily Rhodes gets kicked out of boarding school and runs away to Los Angeles, reconnecting with her parents, Rick and Cece, and sister, Carol. Back in present day, Blair and Nate attend prom together, but the evening doesn't turn out exactly as planned and Chuck and Serena have a little something to do with that. Serena and Lily don't see eye-to-eye over Serena's recent run-in with the law. No Doubt performs in the flashbacks as an 80s band called "Snowed Out".

The guys' plan to work over the summer at the North Pole makes Penny reevaluate her feelings for Leonard.

Week 10 finds only four dancers remaining as they have two new dances to learn.

Tony, Stella's fiancé, makes an attempt to ease the burden he feels for "ruining Ted's life", by helping him find a job, but instead proves that no good deed goes unpunished. Meanwhile, Barney wants to prove that he can get out of a speeding ticket.

Jack and the FBI must secure the biological weapon before it is released on the subway, Olivia is forced to make the transaction on Jonas Hodges murder in order to be protected, and Kim suspects she is being followed at the airport. There is friction between Chloe and Janis at the FBI. Later, Jack is forced to help the terrorists in order to protect someone close to him.

Allison struggles with her decision to switch jobs. When continues to have visions about a serial killer she is forced to choose between honoring the contract with her new job and sharing her information with the police.

Lucas and Peyton's wedding day finally arrives, bringing some surprise guests along with it. Haley finds herself playing an unexpected role in the ceremony, as Skills and Brooke try to control Jamie and Nick. Meanwhile, Nathan continues to hope to be drafted into the NBA.

Charlie seeks to take advantage of Alan and Chelsea's budding friendship.

A new pilot endangers the helicopter when he becomes reckless. Bad weather delays the aqua loggers; and a greenhorn attempts to prove himself.

Jeff doesn't get any dinner after someone else eats it before Jeff does now he has to keep quiet about it.

Horatio's team investigates the murder of a man who was boiled alive. Meanwhile Julia loses control and one of the teams darkest secrets gets out.

After falling into a coma during an investigation, Allison's spirit finds it's way into the body of a man named Todd Emory. Joe and the kids have to adjust to living with Allison's spirit in the body of Todd, who insists on living with them.

Lauren is put into an awkward situation after Stephanie messes up at work. Meanwhile, Justin calls out Audrina for hooking up with Brody.

Castle and Beckett investigate the murder of a plastic surgeon. Meanwhile, Alexis has her first prom and Castle snoops around Beckett's past and it's up for a surprise.

The spotlight is focused on unknown people who go on reality shows to make themselves famous.

The current U.S. Secretary of the Interior, Ken Salazar.

Tonight Stephen welcomes Tamara Draut.

Celebrity Chef Challenge 2 - Martin Boetz

When Hisagi faces off against Findor Carias, his opponent proves to be much stronger than he first thought. As such Hisagi is forced to release his Shikai, Kazeshini in order to defeat him.

Maddy's twin sister Hannah shows up in the AAU needing her help. Donna tries to cheer Michael up. Elliott tries to find out what is wrong with Ben.

What makes ordinary people commit extreme acts of violence? In a thought-provoking and disturbing journey, Michael Portillo investigates one of the darker sides of human nature