In the next episode of the "The Big Bang Theory," Leonard Hofstadter (Johnny Galecki) tries to recall where he kept a potentially lucrative investment.

The synopsis and promotional photos for the upcoming installment titled "The Bitcoin Entanglement" was just released and showed Leonard trying to remember where he placed an important investment using Bitcoins. His wife Penny (Kaley Cuoco), Sheldon Cooper (Jim Parsons), and Amy Farrah Fowler (Mayim Bialik) are there to ask him more about the alternative form of currency. Apparently, Leonard and his friends Howard Wolowitz (Simon Helberg) and Raj Koothrappali (Kunal Nayyar) invested in Bitcoins early on but did not tell Cooper about it. The quirky physicist is offended by this and decides to teach the guys a lesson. It remains to be seen how he will put his friends in their place for not letting him take part in their venture.

Meanwhile, Penny's old friend Zack (Brian Thomas Smith) visits her and Leonard to tell them about a 7-year-old video that he discovered. The couple is intrigued by this as they watch the video together. They realize that the footage reveals a secret about their relationship which they did not know previously. Zack is shown smiling while Penny grimaces with discomfort. It appears that this is one secret Penny would rather have buried in the past.

In the last episode, Cooper went behind his friends' back and accepted a request to work for the military. Leonard and Wolowitz were offended by his secrecy that they decided to get Barry Kripke (John Ross Bowie) to help them with their project without telling him. Cooper realized his betrayal and told them that everyone should be honest from now on to avoid any misunderstanding.

"The Big Bang Theory" season 11 episode 9 will air on Thursday, Nov. 30 at 9 p.m. EST on CBS.