After Leonard tries to help Penny following a failed role on a TV show, she makes an important decision. Meanwhile, Raj and Stuart try to practice their social skills, and Sheldon navigates the intricacies of being funny.
Sheldon tries to relax after he is forced to take a vacation. Leonard struggles to be supportive of Penny after she quits her job. Amy receives unwanted attention from a co-worker. Bernadette seeks Stuart's help in replacing one of Howard's comic books.
When the guys can't get hold of any Comic-Con tickets, Sheldon tries to hold his own convention and ends 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 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.
Leonard's purchase of a dining room table causes Sheldon to reevaluate the changes in his life. Meanwhile, Howard is offered a chance to go back to space and Bernadette struggles with whether or not to encourage him.
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 mother in Houston, he is forced to confront a new reality. Back in Pasadena, the rest of the gang reluctantly take part in Raj's Murder Mystery party.
While Raj is wracked with guilt when he tries to date Lucy and Emily at the same time, Penny wrestles with whether to take a role in a cheesy movie and Sheldon is torn trying to choose between two gaming systems.
Penny tries to help Sheldon when he reconsiders his "relationship" with String Theory. During a dinner with Howard and Bernadette, Raj discovers Howard once embarrassed himself on a date with Emily.
When Sheldon tries to be spontaneous, it leads to unexpected friction between some of the gang. Meanwhile, Raj seeks Howard's help in preparing for a date with Emily.
Penny gets fired from her movie and takes a serious look at her life. Raj sees Emily on a date with another man at the movies. Howard and Bernadette have to take care of his mother after she breaks her leg.
Sheldon gets upset about his career, the destruction of the comic book store and Leonard and Penny's future living arrangements. Howard and Bernadette struggle to keep hold of a caregiver for Mrs. Wolowitz.
Sheldon's trip comes to an end when he is robbed, Penny interviews for a job at Bernadette's company, and Howard is weirded out by his mother's relationship with Stuart.
Howard becomes nervous after NASA asks him to throw out the first pitch at a Los Angeles Angels game. Meanwhile, Leonard and Penny try to prove Sheldon wrong when he says that he and Amy have a 'superior' relationship.
Raj's honesty about his past comes back to haunt him after Emily takes a dislike to Penny. Meanwhile, the guys consider investing in the comic book store.
Sheldon and Raj test whether they could survive a dark-matter research expedition in a salt mine by simulating the conditions in a steam tunnel. Meanwhile, Leonard and Penny seek advice from Howard and Bernadette when they argue about money.
The guys befriend one of Penny's clients when he shows up at her apartment. Meanwhile, Bernadette gets upset when Amy torpedoes an article about her for a local magazine.
The girls decide to re-enact their high school proms with the guys. While Sheldon feels under pressure to commit to his relationship with Amy, Howard worries about who Stuart will bring as his date.
While Sheldon retires "Fun With Flags", Leonard, Howard and Raj look for something significant in a dead professor's research, and Bernadette finds out what her colleagues really think of her.
Amy hosts a traditional Victorian Christmas Eve dinner as Raj's father comes to visit, while the guys try to shoo out a bird they let into the university clean room.
