Jim Parsons
Actor Jim Parsons arrives at the 22nd Screen Actors Guild Awards in Los Angeles, California January 30, 2016.Reuters

Monday's episode of The Big Bang Theory is titled The Hot Tub Contamination and it will see Sheldon opening up about his past to Penny.

Warning: This post contains spoilers from the upcoming episode of The Big Bang Theory.

According to a description of The Hot Tub Contamination on The Big Bang Theory wikia, the episode will see Amy and Sheldon, who are living together, fighting about the bathroom schedule Sheldon wants her to stick to. They come to Leonard and Penny for a solution to this problem, and from the looks of it Amy is wondering if it was a good idea to move in with her boyfriend.

Later, when Sheldon is discussing the challenges of living with Amy, he reveals the real reason why he knocks three times before he enters a place. It so happens that Sheldon once walked in on his father having sex with someone other than his mother, and he now wants to avoid witnessing a similar scene. While the first knock is to alert the person that someone is at the door, the second and third is to give the person inside a chance to pull up his pants.

Elsewhere in the episode, viewers will see Bernadett and Howard deciding to take a mini vacation before their baby arrives. But Bernadette, who now has a visible baby bump, will not be feeling well enough to travel, forcing them to cancel their plan.

The Big Bang Theory airs Mondays on CBS. The synopsis for Season 10 episode 5 reads: "Sheldon and Amy try to work out their problems created by living together, while Howard and Bernadette take a vacation. Raj and Stuart use their hot tub."

New episodes can be watched via CBS All Access.