The boys will run into trouble when they try to surprise Leonard (Johnny Galecki) with a road trip to Mexico and a belated bachelor party on Monday's episode of "The Big Bang Theory."

In the episode, titled "The Bachelor Party Corrosion," the geeky gang will run into a few problems along the way.

In the meantime, Amy (Mayim Bialik) and Bernadette (Melissa Rauch) will try to convince Penny (Kaley Cuoco) to tell her family that she has eloped with Leonard. According to the episode's synopsis, Keith Carradine will reprise his role as Penny's father Wyatt, reports SpoilerTV.

In the last episode, Leonard and Penny were finally able to work past their marital woes over Leonard's confession that he kissed his coworker Mandy (Melissa Tang) two years before. After speaking to Mandy about the incident, Leonard realized that he was trying to sabotage his relationship with Penny in fear that he was not good enough to be with her. He and Penny then discussed their insecurities in their relationship and made up, reports Fox News.

Meanwhile, Sheldon (Jim Parsons) continued to try to win Amy back. When his efforts failed, he became frustrated and decided to instead bad mouth her on his web series "Fun With Flags."

The synopsis for the next episode reads, "The guys' science skills are put to the test when they get a flat tire during Leonard's bachelor party weekend in Mexico. Also, the girls force Penny to finally tell her family that she eloped with Leonard."

A video promo of the new episode also reveals that Amy will consider getting a makeover, while Sheldon seems to be reluctant to go on the road trip with the guys. As a result, they force him into their van and tie him up. Watch the clip below.

Season 9 Episode 3, "The Bachelor Party Corrosion," will premiere on Monday, Oct. 5 on CBS.