Big Mouth

Third-class lawyer Park Chang-ho (Lee Jong-seok) is on the brink of divorce from his wife Go Mi-ho (Im Yoon-ah) after being scammed.

Chang-ho (Lee Jong-suk) wakes up in the hospital and is charged with drug use and is imprisoned in Gucheon Prison. By the way, is Park Chang-ho a rare genius con artist Big Mouse?

Who the hell made me Big Mouse? One thing is clear, that Miho (Lim Yoona) can only be protected by being recognized as a Big Mouse.

Is Chang-ho (Lee Jong-suk) the real Big Mouse? Gong Ji-hoon (Yang Kyung-won) proposes a bet to find out Chang-ho's identity...

Chang-ho (Lee Jong-suk) has an interrogation with a witness who knows important information about Big Mouse, and Ji-hoon (Yang Kyung-won) and Do-ha (Kim Joo-hyun) watch it nervously. Meanwhile, Ji-hoon approaches Mi-ho to find Seo Jae-yong (Park Hoon)'s thesis through Mi-ho (Im Yoon-ah), but does Mi-ho know the identity of Park Chang-ho? Or is he being deceived?

Did Chang-ho (Lee Jong-suk) deceive even Mi-ho (Im Yoon-ah)? Miho, who joined the prison medical volunteer work to meet Chang-ho, is unfamiliar with Chang-ho, who is receiving special treatment in prison.

Jae-ho (Lee Yoo-jun) warns Chang-ho (Lee Jong-suk) not to listen to Seo Jae-yong (Park Hoon)'s thesis. Mi-ho (Im Yoon-ah), who is one step closer to the thesis, is attacked by a monster.

Park Chang Ho (Lee Jong Suk) is imprisoned in a mental hospital. Can Chang Ho hide his identity in a state of confusion?

Chang-ho (Lee Jong-suk) goes directly to the informant of the murder trial of Seo Jae-yong (Park Hoon) through SNS live, and Ji-hoon (Yang Kyung-won) and Jung-rak (Jang Hyuk-jin) track Chang-ho in real time.

Chang Ho (Lee Jong-suk) called Big Mouse, and he responded. An unexpected person appears at the promised time...

Chang-ho (Lee Jong-suk) turns the game of power in the prison and begins to tighten Big Mouse's neck. Doha (Kim Joo-heon) also planted a new warden and tried to find Big Mouse.

Taking advantage of the chaos of the entire prison due to the riot, the warden plans to eliminate Chang-ho (Lee Jong-suk) and Mi-ho (Im Yoon-ah).

Chang-ho (Lee Jong-seok) visits Chairman Kang and makes a proposal that can shake his heart, and Do-ha (Kim Joo-heon), who was bothered by such a thing, joins hands with Yoon-gap (Jung Jae-seong) and plans to get rid of Park Chang-ho.

Chang-ho (Lee Jong-seok), with the help of Ji-hoon (Yang Kyung-won), is about to start a full-fledged election battle with Doha (Kim Joo-heon), but a red light comes on for Mi-ho (Lim Yoon-ah)'s health.

The TV debate begins, and the smoking gun that will bring down Choi Doha is at Miho's fingers.