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.