Leonard becomes concerned when his date with Penny ends abruptly and she starts blowing him off. When told the truth, Sheldon would rather move out than keep Penny's reasons a secret from Leonard.
Penny plans revenge when Sheldon bans her from his and Leonard's apartment, while Howard and Raj use the latest technology to try to find the house being used in "America's Next Top Model."
Leonard tries to slow down his relationship with Stephanie when he realizes that they are living together, while Sheldon becomes convinced that he has an untraceable disease.
Leonard is disappointed when Penny develops an interest in an attractive physicist at the university. Meanwhile, Sheldon struggles to find an appropriate Christmas gift for Penny.
Howard becomes depressed after Penny makes a cruel statement about his love life, while the rest of the guys prepare for a grudge killer robot duel against an obnoxious colleague at the university.
On a train to San Francisco, Howard, Raj and Leonard fight for the affections of sci-fi star Summer Glau, while Sheldon is forced to turn to Penny for help when he leaves his flash drive behind.
Leonard is upset when the owner of the comic book store goes on a date with Penny, so he convinces Howard and Raj to take him to a bar so that he can pick up a woman of his own.
After being dumped by Leslie, Howard heads to Las Vegas with Leonard and Raj. Meanwhile, Penny is forced to take in Sheldon after he locks himself out of his apartment.
