Sheldon protests when the gang drags him to Mrs. Wolowitz’s house for Thanksgiving. Meanwhile, Penny and Leonard must deal with a mistake from her past.

When the entire gang competes in a scavenger hunt designed by Raj, it brings out the best - and worst - in everyone.

Sheldon's latest scientific breakthrough leaves him feeling like a fraud; a romantic gesture between Howard and Bernadette causes Penny to up her game with Leonard.

Sheldon and Amy take a train ride to Napa Valley with Howard and Bernadette on Valentine's Day. Leonard and Penny take Raj's dog to the vet when she accidentally eats some chocolate.

While Sheldon is at home in Texas, the rest of the gang realizes how much he has changed their lives as they decorate the apartment Christmas tree.

While Raj is wracked with guilt when he tries to date two women at once, Penny wrestles with whether to take a role in a cheesy movie and Sheldon is torn trying to choose between two gaming systems.

After the guys can’t get Comic-Con tickets, Sheldon tries to hold his own convention and winds up spending a wild night with James Earl Jones. Meanwhile, the girls try to feel more mature by going to a fancy hotel for tea.

Sheldon faces a personal crisis after deciding he’s wasting his time with string theory. Meanwhile, a double date between Raj, Emily and the Wolowitzes ends in embarrassment for Howard.

Sheldon get upset about his career, the destruction of the comic book store and Leonard and Penny's future living arrangements. Howard and Bernadette can't keep hold of a caretaker for his mother. With his entire world changing around him, Sheldon considers a major move.

Leonard and Sheldon's friendship is tested; Howard's latest foray into helping his mother has some disastrous side effects.

Sheldon gets mad at Amy for ruining one of his favorite movies, Raj and Stuart try to make their online dating profiles more appealing, and Leonard tries to play the sympathy card with Penny.

A bad day causes Penny to reevaluate her life choices – including Leonard. Meanwhile, Howard and Bernadette struggle to care for Mrs. Wolowitz, and Raj gets relationship advice from Sheldon.

With Leonard away, Sheldon and Penny spend quality time together sharing intimate secrets. Also, Wolowitz helps Raj get over his ex-girlfriend.

Sheldon seeks payback when Arthur "Professor Proton" Jeffries asks Leonard for help on a project instead of him. Raj gets upset at Howard for crashing his night with the girls.

As the gang celebrates Star Wars Day, Sheldon has difficulty dealing with the recent death of Arthur "Professor Proton" Jeffries.

Amy starts working at Caltech which causes friction with Sheldon. Howard agrees with Sheldon who mentions this to Bernadette causing a big fight for the Wolowitzes.

Leonard has to deal with the fallout of disproving Sheldon's new scientific discovery. Raj spends a week at Howard and Bernadette's apartment.

Leonard buys a dining room table and it causes Sheldon to reevaluate the changes in his life. Meanwhile, Wolowitz is offered a chance to go back to space and Bernadette struggles with whether or not to encourage him.

When a mistake comes to light, Sheldon makes Leonard walk a mile in his shoes; Penny decides to confront Raj's ex-girlfriend, Lucy.

Sheldon tries to relax after he is forced to take a vacation. Meanwhile, Leonard struggles to be supportive of Penny after she quits her job, and Bernadette seeks Stuart’s help in replacing one of Howard’s comic books. Also, Amy receives an unwanted attention from a co-worker.

To prepare for a date with Emily, Howard acclimates Raj to horror movies. Penny and Sheldon are upset when they discover Amy and Bernadette lied to avoid hanging out with them.

When Penny’s big acting break on NCIS is a bust, Leonard struggles to help her, which results in Penny asking Leonard a bold relationship question. Meanwhile, Raj and Stuart try to practice their social skills, and Sheldon navigates the intricacies of being funny.

After arguing with Sheldon, Howard tries to make amends by taking him to NASA headquarters in Houston. Penny has second thoughts about quitting her waitressing job when her car dies. Amy gets involved in trying to find Raj a date.

When Sheldon visits his Mom in Houston, he is forced to confront a new reality. Meanwhile, Raj’s ‘Murder Mystery’ party starts some fights within the gang.