Leonard and Penny will finally walk down the aisle and get married in the season 9 premiere episode of "The Big Bang Theory", a leaked synopsis of the episode revealed.

The premiere is entitled "The Matrimony Momentum" and it will see the duo at a Las Vegas wedding chapel picking out their wedding package. Their friends gather at Bernadette and Wolowitz's house to watch the wedding ceremony online, but they miss out the important moments when Amy and Sheldon get into a fight.

The previous season of "The Big Bang Theory" ended with Amy breaking up with Sheldon saying she wanted to take a step back and analyse their relationship. But the upcoming season will see Sheldon having a hard time coming to terms with Amy's decision, and it will result in him passing a few condescending remarks that will tick off Amy even more.

This prompts Amy to finally break up with Sheldon for good. Although Stuart tries to hit on Amy, she doesn't seem interested.

"It's a very funny episode," Mayim Bialik wrote about the premiere episode in Kveller.com. "It doesn't tie everything up in a neat package; our show rarely does that. It's a lot of group scenes, and some really good one-on-one scenes as well. Kevin Sussman ("Stuart") is back with some lines that are making me crack up in rehearsal already. It's a great season opener."

As for the newly married couple, their relationship gets strained when Leonard admits that the girl he kissed works with him. Later, Sheldon reveals to Penny that the girl Leonard kissed is both smart and attractive.

"The Big Bang Theory" returns to CBS on 21 September. According to the show's wiki page, the summary of "The Matrimony Momentum" reads: "Leonard and Penny arrive in Vegas while the gang unite at the Wolowitz house to watch the wedding online. Sheldon pushes Amy to make up her mind about the status of their relationship."