The Wolowitzes' life gets complicated when Stuart starts bringing his new girlfriend home. Also, Penny and Leonard talk about starting a family while Koothrappali explores an arranged marriage.
Sheldon won't tell anyone why he's never mentioned Tam, his childhood best friend, so Leonard takes matters into his own hands. Also, Bernadette and Penny take out Raj's fiancée, Anu, for dinner to get the skinny on her.
Amy doesn't have time to work with Sheldon on super asymmetry, so he goes to great lengths to ensure she's available. Koothrappali doesn't want Wolowitz to join him in hosting a show at the planetarium.
When Wolowitz dresses up as Sheldon for Halloween, Sheldon seeks retaliation at Leonard and Penny's Halloween party. Also, Leonard is shocked that Penny doesn't remember their first kiss.
Leonard is caught between a rock and a hard place when he's responsible for distributing extra grant money. Also, Bernadette turns the backyard playhouse into a hideaway from her husband and kids.
Sheldon tries to bond with Amy's father, but when Wolowitz lures Mr. Fowler away with magic tricks, Sheldon has no choice but to bond with Mrs. Fowler. Also, Koothrappali and Anu try to get physical for the first time.
Sheldon and Amy are devastated after learning from a Russian paper that super asymmetry has already been theorized and disproved. Bernadette wants to beat Howard in a popular video game.
A VHS tape from Sheldon's past inspires him and Amy not to give up when they're still feeling down about their theory being disproven. Bernadette turns into a pageant mom when she tries to help Howard with his Magic Castle audition.
Penny and Leonard organize a paintball game, which results in mayhem when Sheldon becomes jealous of Amy. Raj catches Anu with her ex-boyfriend. Stuart doesn't want to move in with Denise.
Sheldon and Amy are thrilled when their super asymmetry theory is proven by two physicists, until they try to kick Amy off the Nobel nomination. Bernadette gets one of her drugs approved and wants a reluctant Penny to head the sales team.
Sheldon is thrilled to help Bernadette and Howard navigate bureaucracy concerning a neighbor's non-compliant balcony until he learns they too have ignored codes. Leonard is disappointed when his friends are uninterested in his new laser.
Penny tries to throw a wrench into Leonard's plan to be a sperm donor for her ex-boyfriend; Wolowitz, Bernadette, Anu and Koothrappali turn Koothrappali's canceled bachelor party into a couple's trip aboard the "vomit comet."
The gang finds out Wil Wheaton hosts a celebrity Dungeons and Dragons game involving William Shatner, Joe Manganiello, Kareem Abdul-Jabbar and Kevin Smith. Deception and betrayal are the path to make it to the one open seat.
Bernadette and Penny travel to San Diego for a pharmaceutical sales convention. Back home, Amy and the guys experiment on the Wolowitz children when Sheldon finds a book on it.
Rivals Pemberton and Campbell charm America on a publicity tour so Sheldon and Amy try to win over Nobel laureates Kip Thorne, George Smoot and Frances Arnold. Halley's fear of the dark causes opportunity and conflict at the Wolowitz home.
Contemplating what it would mean to all women if she were to win a Nobel Prize causes Amy to have a meltdown. Koothrappali and Wolowitz try to relive the good old days after Wolowitz buys a scooter that looks like the one he had years ago.
Koothrappali is worried people won't take him seriously in his own field after publishing a paper that suggests he may have discovered alien life. Leonard wants to be the principal investigator on a plasma physics study.
Kripke has proof that Dr. Pemberton plagiarized his thesis in college, and Sheldon and Amy aren't sure if they should turn him in. Wolowitz learns that Bernadette wasn't the only waitress at the Cheesecake Factory who had a crush on him.
Leonard is pleasantly surprised when Beverly comes to visit and she's genuinely kind to him, until he finds out the real reason she's there. Also, Denise and Stuart overstay their welcome at the Wolowitz house.
Bernadette and Wolowitz leave their kids for the first time; Penny and Leonard try to keep a secret; Sheldon and Amy stick together; and Koothrappali makes a new friend, as the gang travels together into an uncharted future.
