With his friends on dates, Raj must face his loneliness. Also, Wolowitz is caught in an argument between Bernadette and his mom, even while he’s in space.

Raj and Howard try to to figure out why Sheldon disappears at 2:45 every afternoon; jealousy arises in Penny and Leonard's relationship.

The guys search for a perfect Valentine's Day gift for their significant others; Stuart and Raj host a "lonely people" party at the comic book store.

When Leonard receives an exciting opportunity to work overseas, Penny and Sheldon are thrown for a loop. Raj and Lucy's relationship comes to a crossroad.

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.

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

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.

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.

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.

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.

Leonard and Amy make an unexpected trip to Arizona to fetch Sheldon; Penny interviews for a job at Bernadette's company; Stuart's relationship with Mrs. Wolowitz disturbs Howard.

The girls head to Las Vegas for some weekend fun, while the guys try to invent something cool, but only come up with new ways to procrastinate.

When Leonard gets minor surgery on his nose, Sheldon is the one in need of sympathy. Meanwhile, Raj's parents' impending divorce causes Howard and Bernadette to work on their own marriage.

When Sheldon becomes stuck in a rut with his work, the gang tries to help him by raising his stress levels. Howard teases Raj with a game called "Emily or Cinnamon?"

As a joke, Sheldon and Penny try an experiment designed to make participants fall in love. Meanwhile, Leonard, Amy, Raj and Emily spend the evening trying to escape a room with a “zombie.” And, after returning from Mrs. Wolowitz’ funeral, Bernadette and Howard run into trouble at the airport.

When Raj is asked to create a message in case a NASA mission discovers alien life, the guys fight over what he should do. Also, Penny is torn between auditioning for a movie or keeping her successful pharmaceutical sales job.