Faced with an uncertain future, Sheldon considers a major change; Emily and Raj decide to take things to the next level. Also, Howard and Bernadette struggle to care for Mrs. Wolowitz when she is injured.
Episode: 24
The Bon Voyage Reaction
When Leonard is considered for an exciting research opportunity, Sheldon becomes jealous and tries to scare him into backing out. Meanwhile, Raj's relationship with Lucy is strained when he tries to get her to meet his friends.
The Countdown Reflection
As Howard's mission to space approaches, Howard and Bernadette decide to get married before his launch, causing the gang to scurry into overdrive in an effort to stage the wedding.
The Roommate Transmogrification
When Bernadette receives her PhD, Wolowitz feels emasculated. Raj and Leonard swap apartments and Penny does something she regrets.
Revival
While Higuchi is finally captured, Light inadvertently regains his memories as Kira.