Sheldon and Raj will be forced to endure intense heat while being trapped with each other when they go on an underground adventure in the name of science in Monday's all-new episode of "The Big Bang Theory."

In the last episode, Penny, Amy and Bernadette took an all-girls trip to Las Vegas while the boys tried to plan a productive weekend without their girlfriends, reports Fox News. Instead, they ended up getting sidetracked by Google and 80s movies, which help them realize that their girlfriends aren't as distracting as they originally thought.

In the upcoming episode, which is titled "The Expedition Approximation," Sheldon and Raj agree to work in a mine together. However, Penny warns them that they are not prepared to work in a mine.

"You guys are going to work in a mine? You had a panic attack when we went through the car wash," snaps the snarky blonde in a promo video.

Fortunately, the plot will give viewers the opportunity to see Sheldon and Raj interact with one another since the two characters aren't typically paired off on the show, notes CarterMatt.

In another scene from the teaser video, Leonard seems to get offended when Penny points out one of his insecurities.

"I can't believe you'd say that," he tells Penny. "You know how insecure I am about my insecurities."

In the meantime, Leonard and Penny are going to face new challenges now that Penny has landed a new high paying job.

CBS series released an official synopsis of the new episode:

"Sheldon and Raj test whether they could survive a dark-matter research expedition in a salt mine by simulating the conditions in a steam tunnel. Meanwhile, Leonard and Penny seek advice from Wolowitz and Bernadette after they fight about money."

A teaser video also announced that this may be the last episode of "The Big Bang Theory" that falls on a Monday.

"The Big Bang Theory" Season 8, Episode 6, "The Expedition Approximation," will air on Monday, Oct. 20, at 8 p.m. ET on CBS.

Watch a teaser video below.