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.
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.
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.
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.
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.