Season 9 episode 4 of "The Big Bang Theory" will see Sheldon trying to find a new roommate after Leonard and Penny take the next step in their relationship and move in together.

Click here to watch the episode online.

The episode's title, "The 2003 Approximation", appears to be a reference to the year Sheldon and Leonard moved in together.

According to the extended plot summary of the episode on "The Big Bang Theory" wikia page, Sheldon will force Leonard to sign a document that will officially remove him as a roommate, and there will be an emotional moment when Leonard confesses that moving out was harder than he expected.

However, Sheldon's lack of understanding will ruin the moment.

Viewers will also see Sheldon expressing some of his insecurities, one of which is the fear that Amy will find someone better than him. This fear could be one of the reasons why he even offers Amy a chance to move in with him. But Amy declines.

In the end, Penny will feel bad for Sheldon and she'll suggest that they all try living together. Sheldon readily agrees and makes plans to spend the Fourth of July together.

" Yeah! I'm always happy when you come though the door, I'm scared of fireworks..oh and Fourth of July we are all sleeping here (pointing to his apartment)," Sheldon says.

Elsewhere in the episode, viewers will see Howard and Raj trying to form a band when Stuart points out that his comic book store will be more successful if a band played there occasionally.

The official synopsis of "The 2003 Approximation" reads:

Leonard and Penny finally move in together leaving Sheldon very upset with this big change in his life and wishing he could go back to a time when he had no emotions in 2003 before he met Leonard. Raj and Howard attempt to form a band.

"The Big Bang Theory" is aired Mondays on CBS.