When "The Big Bang Theory" season 10 returns to be the small screen, Sheldon (Jim Parsons) will reveal a surprising secret to Penny (Kaley Cuoco).

Titled "The Hot Tub Contamination," episode 5 will see Sheldon and Amy (Mayim Bialik) continue to struggle with the adjustments now that they live together.

The couple will be dealing with the conflicts on their bathroom schedule, and neither of them is willing to at least find the middle ground, prompting Penny and Leonard (Johnny Galecki) to help.

In a leaked synopsis by a source whose track record with plot spoilers has been proven credible, Penny and Sheldon will hang out in this episode.

At some point in "The Big Bang Theory" season 10 episode 5, he tells her that being with Amy has unleashed the "sexual creature" within him.

This is why "The Big Bang Theory" season 10 episode 5 will see Sheldon make an attempt to hit on some women at the ice cream parlor, although he was not attracted to any of them.

At some point during their stay there, Sheldon opened up to Penny about a secret he never told anyone — about how when he was a boy, he went home early to find his father in bed with another woman while his mother was in bible study.

Sheldon and his father never talked about what happened after that. Episode 5 will not get into the bombshell much, though, as it will no longer be mentioned in the episode.

By the end of the episode, Sheldon and Amy will resolve their differences and will soon agree to share the toothbrush holder.

As for Howard (Simon Helberg) and Bernadette (Melissa Rauch), they will learn in this episode that Raj (Kunal Nayyar) and Stuart (Kevin Sussman) have been sneaking into the house to use the bathtub when they know the couple will not be home.

"The Big Bang Theory" season 10 episode 5 is scheduled to air on Monday, Oct. 17, at 8 p.m. ET on CBS.