The guys are coming home from the North Pole, but only Sheldon is satisfied with the trip, while the rest don’t have very good opinions. Inside their room, Sheldon is shocked to learn that the guys tampered with his data from the experiments he performed, and when nobody seems to understand how sad or furious he is, he leaves to Texas in disgrace. Meanwhile, Penny is more than happy to see that Leonard has come home, and their relationship goes to a whole new level when Penny kisses him incessantly.

It’s comic-book-night for the guys, but they are surprised to see Leonard there. Howard and Raj were expecting him to be having sex with Penny, but as Leonard reveals only to get them off his back, the previous night they spent together was “just fine”. When Sheldon brings this up during a normal conversation, it shocks Penny what Leonard actually tells the guys. Meanwhile, when Howard and Sheldon hear a cricket in the apartment, they start arguing about what species the cricket belongs to, and end up betting their best comic books against each other.

Sheldon is getting sick of Penny’s misbehavior, and decides to do something about it. He uncovers that Penny has a “thing” for chocolate, and decides to use it in order for her to get a better mood and behavior towards him. Meanwhile, Raj and Howard want to pick up women, and their newest attempt has them dressed like Goths and going to a Goth nightclub, where they try to impress the women, but it doesn’t go flawless.

It’s a typical day for the boys until Raj runs out of the apartment crying. Howard decides to talk to him and when he comes back, he brings the worst news ever: Raj is getting deported. The only way he can avoid deportation is to get a new job, and he goes as far as agreeing to work for Sheldon in order to remain in the country. Meanwhile, Leonard and Penny try to get some time for themselves, but have to deal with Howard as a third wheel.

Penny loses in a card game, but is surprised when it turns out Sheldon has a special gift in those sorts of games; he can calculate what the opponent’s cards are just from his mind. Afterwards at the comic book store, Sheldon is positively shocked to learn that Wil Wheaton is entering the same card game that Koothrappali is in, and he agrees to be Raj’s partner. Meanwhile, Howard persuades Penny into hooking him up with one of her friends.

The guys are going outside to play with kites, but Leonard meets with Penny down the stairs and feels jealous when Penny tells him that she is going to have a friend over and watch football (something Leonard doesn’t understand). However, Leonard discusses the matter with Penny and end up needing to learn the rules of football, but his only choice for help is Sheldon. Meanwhile, during a kite competition between Howard and Raj, Howard leaves to chase a girl, leaving Raj angry at him.

Leonard, Penny and Sheldon are playing a game that Sheldon created himself, but there’s more than just the game going on when Leonard and Penny start arguing loudly about Leonard being jealous than Penny’s old “friend” is going to sleep on her couch through the weekend. However, when the anger between Leonard and Penny continue over to Howard and Raj, the whole group is almost divided; Sheldon (the only one not involved in any fight) takes the position of peacemaker.

Leonard, Howard and Raj are on a camping trip in the desert to see the Leonid meteor shower, while Sheldon is at home enjoying the thought of being alone. But his night takes a turn when Penny needs medical help when she fell in the shower and dislocated her shoulder, making Leonard her only rescue. Meanwhile, the guys in the desert are drunk and accidentally eat their way to being foodless.

Sheldon decides to use his great mind to come up with the perfect prank to pull on Kripke after he was humiliated on National Radio because Kripke had put helium in Sheldon’s office (making his voice girly while on the radio). However, Sheldon uses many attempts, but can’t come up with a great scheme to pull back on Kripke, until a science experiment comes to his mind (which involves dropping lots and lots of foam from the ceiling right down on Kripke while recording the video to YouTube). Meanwhile, Howard is unsure if he wants to continue his relationship with Bernadette when he finds out she wants a commitment while he just wants sex.

Howard has regrets about introducing Bernadette to the others when she and Leonard really start to get along; forcing him into an uncomfortable position in which he will do anything to separate them again. Meanwhile, Penny sees the connection between Bernadette and Howard and she wants to learn what Leonard’s job really is about. However, her only choice for help is Sheldon, who isn’t the best teacher for those not so interested in science.

Leonard’s mother, Beverly, returns for another visit. Leonard is still not pleased with her coming over, while Sheldon is ecstatic. Penny, however, stresses over the fact that Leonard hasn’t told his mother that he is in a relationship with Penny, and she waits for the perfect moment to tell her, which seems to only be when Beverly becomes drunk for the first time. Meanwhile, Sheldon and Leonard are having friendship issues when it turns out Sheldon has been keeping frequent contact with Beverly while Leonard has been left out, and the most surprising event of this season of The Big Bang Theory: BEVERLY KISSES SHELDON!

When Leonard and Howard go on a double date with Penny and Bernadette, Rajesh becomes the fifth wheel, and decides to seek a hook-up going to a university mixer accompanied by Sheldon (who was looking forward to spending his time alone, but was dragged alongside Raj.) However, when they score and get two girls back to their apartment, their week takes an unexpected turn. Meanwhile, Leonard learns that Penny believes in psychics, and his frustration over it causes her to dislike him. The only way Leonard can get Penny back now, is to meet the psychic and see how real it is.

Returning from a dinner with the rest of the guys, Leonard and Sheldon are shocked to get back to a robbed apartment. Fearing the criminals will return, Sheldon becomes paranoid and locks himself in his room during the night. Realizing something has to be done, they get help from Howard and Rajesh in order to create a state-of-the-art security system that will attack any criminals that try to enter their apartment in the future. However, the security system can't help Sheldon's paranoid reaction to the breaking-and-entering, causing him to move to Bozeman, Montana, but will he return?

When Sheldon starts suffering from "theorist's block" and can't complete a formula, he becomes depressed and is willing to do anything to find the right answer. He tries several techniques to find the answer, but none of them works, but when he figures out how to figure the answer out, he starts working at the Cheesecake Factory with Penny (much to her dismay). However, it turns out Sheldon is like the perfect employee, even passing Penny in the number of customers.

After being invited to Switzerland to see the CERN Supercollider (the world's largest and highest-energy partile accelerator), Leonard wants Penny to join him on the travel, making it a romantic Valentine's Day getaway. Sheldon becomes shocked that he can't go when he has a far bigger interest in the science, and tries to change Leonard's mind in all sorts of ways. Meanwhile, Leonard fears that no matter which of them he'll pick, the other will be angry and he will lose a friendship... or a relationship.

Ruining his one and only chance at meeting Stan Lee, Sheldon winds up in traffic court because of illegal driving that he did when he drove Penny to the hospital (episode 308). However, as Leonard, Howard and Raj are all going to see Stan Lee, Penny is Sheldon's only hope of avoiding jail.

When the guys find a ring from "The Lord of the Rings" at a garage sale, it threatens to tear them apart.

Source: CBS

Sheldon's friends come to his aid when his fear of public speaking stands between him and a coveted award.

Source: CBS

Leonard and Penny's relationship is on the line when they start fighting.

When Leonard and Penny aren't speaking, Sheldon goes to extremes to keep them both happy

Source: CBS

Leonard and Sheldon compete for the attention of a famous female physicist.

Source: CBS

Leonard tells Penny about how he met Sheldon for the first time...and what happened to the elevator.

Source: CBS

While Penny worries that dating Leonard has ruined her for normal guys, Wolowitz and Koothrappali search for Sheldon's perfect match online.

Source: CBS