The Big Bang Theory returns with all new episode this Thursday (13 April), where actor Brian Posehn returns as Bert and introduces his girlfriend, Rebecca, to the gang. Rajesh whines about not having a girl in his life.

Also, Howard and Bernadette have a difficult time leaving their daughter Halley in daycare as her maternity leave is over. Click here to watch the premiere episode via live stream online. You can also click here to watch it online (only in the US).

TBBT season 10 episode 21 is titled, The Separation Agitation, which will air on 13 April at 8pm EST on CBS Network. The official synopsis reads as follows:

Howard and Bernadette have a hard time leaving Halley in day care when Bernadette returns to work. Also, Bert (Brian Posehn) introduces the gang to his new girlfriend, Rebecca (April Bowlby), on The Big Bang Theory.

A promo for the episode shows Sheldon telling Raj what attracted him about Amy, and the answer will surprise the fans. The clip opens with a voice-over that asks, "looking for love?" with Rajesh making a sad face.

Later Leonard asks Penny to find a girl for Raj. "Do you have any friends he can date?" Leonard asks, to which, Penny replies, "I already set up Howard and Bernadette, it's your turn to ruin some poor girl's life."

Later in desperation, Raj is seen asking Sheldon for some advice on dating. He questions Sheldon, "What did Amy have that attracted you? The physicist replies, "Her mind" and later adds, "especially her body", which earns a little tease from Rajesh. However, Amy quickly clears the air and tells everyone, "Relax! We are the same blood type. He knew he can harvest an organ."

The chapter will also feature Sheldon and Amy hosting a special retrospective episode of Fun With Flags with music from Raj and Howard.