‘Big Bang Theory’ Season 9 Spoilers: Episode 22 Synopsis Released; What Will Happen In ‘The Fermentation Bifurcation’?

After taking a very brief break, “The Big Bang Theory” will return to CBS on Thursday and force the gang to confront both their past and future. When a wine tasting separates them, a familiar face returns to ruin their time away in episode 22, “The Fermentation Bifurcation.”

According to the Season 9 episode plot synopsis from CBS, the gang gets the opportunity to go on a wine tasting. While there, they run into Penny’s (Kaley Cuoco) ex-boyfriend Zack (Brian Thomas Smith). Devoted fans will remember that Zack showed up in Penny’s life in Season 3, where he revealed that they once got married in a quickie Las Vegas ceremony. Although she was able to quickly get it annulled later on, he's likely not the person she wants to see while on a romantic getaway with her husband Leonard (Johnny Galecki) and his friends.

As if running into an ex isn’t difficult enough, the gang will struggle with their first introduction to Raj’s (Kunal Nayyar) new girlfriend Claire (Alessandra Torresani). Throughout Season 9, Raj has been struggling with whether he should stay with Emily (Laura Spencer) or try things out with the girl he hit it off with at the comic book store, Claire. Although he’s made his decision, Claire’s introduction to the group won’t go as smoothly as he hopes.

Meanwhile, two members of the cast will be separated from the group going off to the wine tasting. Bernadette (Melissa Rauch) is pregnant, and obviously can’t drink, even if you’re technically just supposed to swish wine in your mouth and spit it out. To make sure she doesn’t feel left out, she’s forced to stay behind with Sheldon (Jim Parsons), for whom the intricacies of a wine tour would likely be lost on.

In a teaser clip for the upcoming episode, Sheldon can be seen finding fun activities for them to do while the others are away, such as making “Star Wars” toast, with one light side and one dark side. Additionally, he digs out his childhood train set to share a story about his youth when he accidentally swallowed a locomotive.

With the group split up tackling problems both emotional and romantic, “The Big Bang Theory’ is poised for a grand return on Thursday night as it begins to close out the last episodes of Season 9.