Penny struggles with Leonard's confession that he kissed another woman as they prepare to get married in Las Vegas. Meanwhile, Sheldon doesn't know what to do after Amy pushes pause on their relationship.
Leonard and Penny try to work through their marital issues. Meanwhile, Sheldon films a special episode of "Fun with Flags" after his breakup with Amy, and Bernadette feels guilty about withholding a secret from Penny.
The guys's skills are put to the test when they get a flat tire on the way to Mexico for Leonard's bachelor party. The girls throw Penny a mini-bachelorette party.
An impending change to his living arrangements inspires Sheldon to revert to 2003, before he met Penny and Leonard. Raj and Howard form a band for the comic book store.
Kripke expresses interest in Amy while leading a fencing lesson for the guys. Meanwhile, Stuart seeks help from the girls in getting more women interested in the comic book store.
Leonard and Sheldon go to great lengths to secure the helium they need during a nation-wide shortage. Meanwhile, the rest of the gang try to find Amy a new boyfriend on a dating app.
While being interviewed for a documentary about Spock from Star Trek (1966), Sheldon struggles to suppress his emotions about his recent break-up from Amy. Meanwhile, Howard and Bernadette butt heads over renovating his mother's house.
Sheldon, Howard and Raj post an ad online to find a new girlfriend for Sheldon. Penny and Bernadette decide to spy when Amy is secretive about who she is dating.
On Thanksgiving, Sheldon and Amy try to spend time together as friends and go to an aquarium, Howard reluctantly agrees to volunteer at the soup kitchen with Bernadette, Raj and Emily, and Penny discovers that Leonard knows more about her than she thought.
Sheldon has a revelation when he realizes why a song was stuck in his head. Meanwhile, Amy invites Dave over for dinner despite their previously awkward date, and Howard and Raj become obsessed with a fan of their band.
Penny gets more than she bargained for when Leonard agrees to meet with a psychiatrist on her behalf to make a sale. Meanwhile, Sheldon and Raj collaborate on an astronomical discovery, and Howard and Bernadette's happiness is short-lived after Stuart moves out.
Sheldon is thrilled when his Meemaw comes to visit, but his excitement quickly fades when she butts heads with Amy. Meanwhile, Raj meets a girl at the comic book store who makes him question his relationship with Emily.
Sheldon and Amy host a Valentine's Day episode of "Fun with Flags", Leonard and Penny grapple with getting older, Howard and Bernadette find a surprise in their hot tub and Raj is torn between Emily and Claire.
Leonard, Sheldon, and Howard run into problems when they file for a patent for their infinite persistence gyroscope. Meanwhile, the girls give Raj dating advice when Emily reaches out to him after their breakup.
Amy is shocked at a revelation from Sheldon after she buys him a new laptop. Meanwhile, Raj sells out Leonard and Howard after they lie to their wives in order to attend an early screening of a movie.
Secrets are revealed when Amy and Sheldon join Penny and Leonard on a weekend cabin trip. Raj is more excited about Howard's and Bernadette's impending parenthood than they are.
Sheldon and Bernadette spend the evening together while the rest of the gang go to a wine tasting party, but things get uncomfortable for Raj when Penny's ex-boyfriend Zack shows up and takes an interest in Claire.
Sheldon hires Stuart to spend the day with Amy when he would rather go to the movies. Meanwhile, Penny struggles to make a connection with Leonard's mother when she comes to visit.
Leonard and Penny try to have a wedding ceremony that everyone can attend, but it creates serious conflict among Sheldon's mother and Leonard's divorced parents. Meanwhile, Howard and Raj become convinced the government is out to get them.
