Big Bang Theory S9 E15
Big Bang Theory S9 E15CBS

"The Big Bang Theory" Season 9 finally has every character coupled up. Thus, the showrunners have a very good reason to indulge in some Valentine's Day fever, which is exactly what fans will get to see in Episode 15, "The Valentino Submergence."

CLICK HERE to watch "The Big Bang Theory" Season 9 Episode 15 live. And, CLICK HERE to watch "The Valentino Submergence" later online.

In Episode 14, we saw Sheldon's favourite person, his grandmother Meemaw, visit him to meet Amy. Initially, she acted cold because she didn't trust Amy because she had initiated the break-up earlier. But as the episode progressed, both Sheldon and Amy managed to convince Meemaw they complete each other. And Meemaw finally came around for the couple.

On the other hand, it was also shown that Raj developed a crush Claire, a bartender working on a sci-fi screenplay for a children's film. He met her at the comic book store where he was with Howard. Claire asked Raj to help her with her story's plot, but Howard and Bernadette warned him against it and said it would upset his girlfriend Emily.

While "The Meemaw Materialisation" was mostly about Amy, Sheldon and their issues with Meemaw, in Episode 15 we don't know who is having the toughest time just around Valentine's Day. The synopsis of "The Valentino Submergence" teases that every couple will be doing something and they all will be facing some problem or the other.

Leonard and Penny will apparently have a major fight as they come to terms about getting older; Howard and Bernadette's romantic plans of getting into a hot tub will be ruined by a special guest. Also, Sheldon and Amy will have trouble while shooting for their web series, and Raj will be all confused between Emily and the cute girl he met at the comic book store.

Meanwhile, the promo clip of the upcoming episode has created a major suspense by hinting that the biggest secret of "The Big Bang Theory" will be revealed in Episode 15.

The official synopsis of Episode 15 reads: "Sheldon and Amy host a live Valentine's Day episode of 'Fun With Flags,' while Leonard and Penny grapple with getting older. Plus, Howard and Bernadette find a surprise in their hot tub, and Raj is torn between Emily and the cute girl he met at the comic-book store."

"The Big Bang Theory" Season 9 Episode 15, titled "The Valentino Submergence", will be aired on Feb. 11 at 8 p.m. on CBS.