In “Big Mouth” Episode 8, Jerry (Kwak Dong Yeon) went looking for Park Chang Ho (Lee Jong Suk) after learning that he had been kidnapped and saved him from Gong Ji Hoon’s (Yang Kyung Won) hands.
Gong Ji Hoon kidnapped Park Chang Ho and committed him to a mental institution. He requested that his 100 million won be returned. They injected the “Truth Serum” into Park Chang Ho with the help of Prosecutor Choi (Jang Hyuk Jin) in order for him to confess where the money and gold were hidden.
Gong Ji Hoon became frustrated as the imposter Big Mouse continued to tell lies. They were about to inject another dose of serum when Park Chang Ho blurted out a location where he had hidden the treasure.
Jung Chae Bong (Kim Jung Hyun), Lee Du Geun (Oh Ryoong), Mr. Choi, and Gong Ji Hoon went to the mountain Chang Ho recommended and discovered a gold nugget underground.
Meanwhile, Park Chang Ho was taken aback by what had occurred. He had no idea real gold had been placed there. He was certain that Big Mouse was keeping an eye on him at the mental hospital.
Park Chang Ho asked Gong Ji Hoon for a meal before continuing their conversation. However, a fire alarm went off at the mental hospital, signalling that Big Mouse had made his move to assist the phony conman.
However, Park Chang Ho had difficulty defeating one of the hospital’s staff members, making it difficult for him to escape. Jerry disguised himself as a firefighter and rushed to Park Chang Ho’s aid.
After they had successfully escaped, Jerry took Park Chang Ho to a remote location and confessed that Big Mouse had paid him to save the imposter. He promised to tell everything, but it was too late because Jerry gave his life to keep Park Chang Ho from being apprehended.
Go Mi Ho was able to persuade Jang Hye Jin (Hong Ji Hee) to accept her offer. Jang Hye Jin approached Gong Ji Hoon and baited him. If he wanted Seo Jae Young’s paper, he needed Han Jae Ho to sign the divorce papers, or else she’d hand it over to Big Mouse.
Park Chang Ho received a message from an unknown number requesting that he visit a specific hotel. It was revealed that the phony Big Mouse met Jang Hye Jin and struck a deal regarding Seo Jae Young’s document.
The VIPs were dragged back to court for their trial thanks to Go Mi Ho, Go Gi Kwang (Lee Ki Young), and Kim Sun Tae (Oh Eui Sik). Park Chang Ho appeared on national television and introduced himself as the informant, ready to roast the VIPs during their trial.