CBS has just released the official synopsis for 'The Big Bang Theory' Season 9 premiere episode titled 'The Matrimonial Momentum,' which will be set in Las Vagas and feature the wedding of Leonard (Johnny Galecki) and Penny (Kaley Cuoco-Sweeting), while Sheldon (Jim Parsons) will be seen dealing with his recent breakup with Amy (Mayin Bialik), reports IB Times.

According to the official synopsis for 'The Matrimonial Momentum,' after driving to Vegas to get married, Penny is seen struggling with Leonard's confession that he kissed another girl while on an expedition. In the 'The Big Bang Theory' Seaon 9 premiere, Sheldon is show as uncertain regarding how he should to act after Amy pushes pause on their relationship. The premiere also brings back Laurie Metcalf Sheldon's mother, Mary.

Earlier, the Hollywood Reporter had revealed the first look at Leonard and Penny's wedding, wherein series show runner Steve Molaro shared some details about the couple's married life. Molaro told the publication, "Chuck and I had a long talk about [revealing the wedding before the premiere] and my fear was that it was going to start sound like they didn't [get married]."

The show runner went on to add, "That was not a positive message - and we didn't want fans to feel like, 'Oh, they're going to pull the rug again and not do it.' There is so much more story beyond that moment that we decided to just let people know."

All said and done, it seems that everything will not be smooth for the newly-weds when Leonard reveals that he kissed Mandy while on a North Sea expedition. Replying to a question on whether Penny is still hurt by Leonard's revelation, Molaro teased, "A little bit, yeah. She thinks she's OK with it and she may not be."

He further stated, "It's the kind of thing that you wouldn't expect to happen and that can be a little jarring. I think when you're Penny, and you have an image that you've cultivated of a person for eight years now and those two things aren't aligning anymore - that can be a difficult thing to deal with."

In the meantime Sheldon, who was dumped by Amy in the 'The Big Bang Theory' Season 8 finale, will not be happy about Leonard and Penny's wedding. Fans are already aware that Sheldon left town after Leonard proposed to Penny, and asked him to move out in the Season 7 final episode. However, now that Leonard and Penny are married, it will be exciting to see what living arrangements they actually work out.

According to Molaro, "Living arrangements are definitely going to be confronted in the first four episodes. It's tricky, sure - Leonard and Penny need to move forward, but at the same time we have a broken-hearted Sheldon), who is sort of their little brother and child and it's tough to ignore that for them."

'The Big Bang Theory' Season 9 premiere episode titled 'The Matrimonial Momentum' airs on Sept. 21 on CBS.