Howard, Bernadette, and Stuart take Halley to the zoo for the final day of Bernadette's maternity leave. All of them, Stuart included, are nervous to send Halley to daycare, and Bernadette feels guilty for getting ready to go back to work.

With Howard away from work, Sheldon thinks it's a good idea to start telling physics jokes at lunch. 

Bert sits down to join them and talks about his new girlfriend. Leonard invites Bert and his new girlfriend to come over for dinner. 

When the two of them arrive, Sheldon points out that Bert's girlfriend is younger and prettier than he is, and notes the similarity to Leonard and Penny. Amy puts him in time out.

The gang quickly realizes that Bert's girlfriend only likes him for his money, and Bert eventually breaks up with her.

Howard and takes Halley to daycare, but he has a hard time letting go. He and Stuart decide to take her from the daycare and spend the day at the aquarium.

Bert is sad about losing his girlfriend, and decides he might buy her a jet ski to get her back. 

Sheldon and Amy film another episode of Fun with Flags -- a retrospective of their retrospective.