
A lawyer with a ten-percent winning rate is caught up in a murder case and becomes the notorious and genius con artist, Big Mouse, overnight. In order to survive and protect his family, he tries to reveal the true colors of the privileged people involved in a huge conspiracy.






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.