The teams take off from their Pit Stop in the Salt Lake City Library and receive a clue telling them to drive to Park City High School where they will find another clue. This clue instructs them to wait until 6 A.M. at which point they will leave in shuttles departing every ten minutes and then help a crew to inflate a hot-air balloon, which they will then ride. In mid-air, the Godlewskis and Weavers have a sort of collision. No real damage is done, but later the Weavers' balloon has a less-than-controlled landing. The teams next participate in a Detour at Heber Valley Railway --- Spike It or Steam It. Most of them choose Spike It, which requires them to accurately construct a section of railway track using old-time tools. The Weavers opt for Steam It in which they fill a tender with 400 pounds of coal. Next the teams travel to Bear Lake Rendezvous Beach, spend the night and then depart fifteen minutes apart. After traveling 137 miles to Dunham, they arrive at Dunham Ranch in Wyoming and participate in a two-person Roadblock that requires them to round-up cattle. Afterwards, they wait for Old Faithful at Yellowstone National Park to erupt, before finally traveling to a ranch at the address 15200 where Phil tells them that they are still racing and they have not arrived at the Pit Stop.

Brennan is about to go out for dinner with her old professor and ex-lover when Booth asks her and her team to help identify the remains of a young woman found in a refrigerator.

House and Chase find themselves in a serious situation after a young mother with stomach pains dies. Months later, Stacy counsels Chase prior to his disciplinary hearing, and must determine whether Chase made a mistake that ultimately led to the patient's death. She soon realizes he is holding something back.

While on duty, McGee kills a man who is later discovered to be an undercover police officer. When Jenny decides to approve the investigation on McGee, the NCIS team is forced to prove that McGee is not guilty, pushing Gibbs' relationship with Jen to the limit. Meanwhile, Tony is troubled by his past.

After weeks of training and careful eating, it comes down to choosing "The Biggest Loser" in this special two-hour, live season finale. Only three contestants remain in the contest to see who has the biggest percentage of weight-loss. The winner will be chosen during the live portion of the telecast.

* Two-hour episode

Cheryl encourages Jim to meet a former girlfriend wants to discuss business for lunch, and then regrets it when she becomes convinced that the old flame has romantic intentions.

As Thanksgiving rolls around, Kate Allen, Mac's mother, comes to the White House for the holiday. Mackenzie invites Templeton and his wife for dinner, which Kate insists on cooking. Meanwhile, Rod brings in Richard "Dickie" McDonald, a media consultant, to help with Mac's image and lagging poll numbers. Mackenzie also must decide the fate of a woman on death row.

When a teenager and her younger sister end up in the hospital after a day at the park, detectives learn that both girls were abducted from New Orleans after Hurricane Katrina along with a third sister who is still missing. Despite the interference of a local reporter, Jackson Zane, detectives are able to catch the kidnapper, a known pedophile, and recover the girl, but when Alvin Dutch dies and the autopsy determines it was Anthrax, Benson puts everything on the line so that she can get the truth out there.

Sean wants Quentin out of the practice after finding out that he's dating Julia. Christian seems to be ok after Kimber leaving him, but his actions indicate otherwise.

TONIGHT: Stephen Colbert welcomes the author of several science books, Richard Preston!