Sheldon's childhood friend from Texas, Tam, is visiting the university with his son. Sheldon does not want to see him and the others wonder why Sheldon has never mentioned Tam. Tam is unaware Sheldon is angry with him, thinking they just naturally drifted apart. Sheldon's brother George does not know the reason either. Sheldon eventually reveals Tam promised he would move to California with Sheldon, but then got a girlfriend and stayed with her, leaving Sheldon feeling abandoned. Tam and Sheldon make up and Sheldon has Leonard take Tam to the airport. Meanwhile, Penny and Bernadette want to get to know Anu, impressed by her connections in the hotel industry. They tell her embarrassing things about Raj and wonder if they can go out with her again after Raj confronts them.
In the third-season finale, Raj and Howard sign Sheldon up for online dating to find a woman compatible with Sheldon and discover neurobiologist Amy Farrah Fowler. Like him, she has a history of social ineptitude and participates in online dating only to fulfill an agreement with her mother. This spawns a storyline in which Sheldon and Amy communicate daily while insisting to Leonard and Penny that they are not romantically involved. In "The Agreement Dissection", Sheldon and Amy talk in her apartment after a night of dancing and she kisses him on the lips. Instead of getting annoyed, Sheldon says "fascinating" and later asks Amy to be his girlfriend in "The Flaming Spittoon Acquisition". The same night he draws up "The Relationship Agreement" to verify the ground rules of him as her boyfriend and vice versa (similar to his "Roommate Agreement" with Leonard). Amy agrees but later regrets not having had a lawyer read through it.
While opening their wedding gifts, Sheldon and Amy cannot figure out the purpose of the glass shard Leonard and Penny gave them. They decide it must be a clue to a scavenger hunt to the real gift. They eventually end up in the coffee shop where they first met and find a locket in the lost and found that they think must be the real gift. The glass shard was actually a crystal chakra wand that Raj gave as a gift to Howard and Bernadette, who then re-gifted it to Leonard and Penny, who finally passed it on as a joke. Leonard and Penny find it less funny when they are given a coded thank-you note they have to use to unlock their WiFi. After making out with his employee Denise at Sheldon and Amy's wedding reception, Stuart finally asks Denise out on a date; while preparing for the date, he has a spray-tan accident, but she just finds it funny and still goes out with him. Raj is depressed everyone else has a relationship and asks his father to arrange a marriage.
Leonard's mother Beverly visits, and he is thrilled when she takes an interest in his work. However, when he learns that she is doing research on him for a new parenting book, he is furious. He prepares to tell her how she let him down over the years, but instead chooses to accept and forgive her, and forgive himself for holding onto that resentment for so long. Beverley is touched that he forgave her and they share a genuine hug. Meanwhile, Anu gets a job offer in London. Raj prepares to fly out and propose to her, ready to follow her if she accepts. Howard stops Raj at the airport, saying there is a better match out there for him, convincing Raj to return home. Stuart and Denise are bothered by her creepy roommate Mitch, while Bernadette and Howard are tired of Denise constantly staying overnight with Stuart at their house. Stuart says he is ready to move in with Denise, and they say they love each other while convincing Mitch to move out.
After Sheldon has a food truck moved away from the building, Leonard and Penny are shocked to find he is the leader and sole member of the Tenants' Association for the building. Amy doesn't want to be caught in the middle but secretly suggests they rally support from the other tenants to vote Sheldon out. Nobody else supports Leonard so Amy tells them Sheldon was never added to the lease when he moved across the hall with her. Sheldon fires back with his own legal technicality so Amy is forced to support Leonard. She makes Sheldon happy by saying he can be Leonard's official opposition, making Leonard believe he made a mistake. Meanwhile, Howard and Raj find a drone. Raj returns it to the cute owner Cynthia and gets her number. Unfortunately, Cynthia watches footage of Raj on the drone and is immediately turned off.
Filming proceeds smoothly – makeup artists do touch-ups, a prop master replenishes the pickle supply – with humor and camaraderie between takes. When a reshoot is needed because Simon Helberg, who plays Howard, held his napkin in the wrong hand, Kaley Cuoco, who plays Penny, lifts her food box high and mockingly asks, “Does it go over my head? I don’t remember.”
Howard and Bernadette learn their second child will be a boy, leading Howard to doubt whether he can be a good father to a son. He and Sheldon go out in the desert to test launch a model rocket, but it explodes, causing him further doubt. On the way home, Howard does a good job coaching Sheldon to drive them home, for which Sheldon tells him he will be a good teacher to his son. Leonard's mother Beverly begins talking to Penny as a friend and confidant, troubling Leonard, especially when he learns that Beverly told Penny that she was proud of her, a level of praise she never bestowed upon Leonard himself. When Leonard confronts Beverly, he is touched when she says that of all of her children's spouses, Penny is the one by whom she is most impressed and that, for this, she is indeed proud of him. Meanwhile, Raj helps Bernadette turn baby girl clothes into boy ones.
It was really hard to pick the right pic for this post, so here is a shot of us in a hug after we filmed the last group scene we would ever film for the series... and TONIGHT is THE NIGHT... it’s the series finale at 8pm EST and then there’s the Young Sheldon (season!) finale, and then a special behind the scenes show hosted by @kaleycuoco and @sanctionedjohnnygalecki and then the entire cast is on @colbertlateshow I hope you get a chance to tune in and i hope you enjoy all of it. If you enjoy it even half as much as we’ve enjoyed (LOVED) creating this show for the past 12 years, then that’ll be a WHOLE WHOLE lot of enjoyment. All of us will miss seeing you in this format, but we will be around in all sorts of ways, I assure you... love love love ❤️❤️❤️
Sheldon needs half a billion dollars to prove his latest concept of string theory, which the University cannot afford to fund. Crowdfunding and selling some of his most valuable comic books to Stuart give him a small start. When Raj mentions gambling in Las Vegas, Sheldon goes there but is caught calculating odds by security before he can make any bets. Meanwhile, Amy takes Penny and Bernadette shopping for her wedding dress. She loves an old-fashioned one that the other girls admit that they find ugly, though Penny assures Amy she can make her own decisions about her wedding. Sheldon, however, comes home and sees Amy in the dress and loves how she looks.