Fueled by the loss of his daughter to a murderer, Detective Oh Gu-tak will use any means necessary to catch criminals, and his ambiguous moral line often results in him getting suspended for
excessive force. After his former superior request him back in the force to track down a serial killer who killed his son, a detective, Gu-tak comes up with a plan to form a team of "bad guys" to work on cases and hunt down the serial killer, ambitious police inspector Yoo Mi-young signs off on the arrangement. Gu-tak releases three convicts from jail to form his team: Lee Jung-moon is the youngest member of
Mensa with a genius
IQ of 165 and
doctorate degrees in math and philosophy, but behind his boyish facade is a
psychopath serial killer; Park Woong-Cheol is a
mob boss who crushed his way to the top of the gangster chain in 25 days, and still remains top dog in prison; and Jung Tae-soo was once a
hired hit man who never made a single mistake, but suddenly confessed and turned himself in one day. In exchange for their collaboration, 5 years of worth of sentences will be reduced for them. When they try to recruit Jung-moon, he escapes captivity and Gu-talk gives Woong-Cheol and Tae-woo the task to apprehend Jung-moon with the reward of 4 years reduction in sentence. In the end, Woong-cheol captures Jung-moon and has his sentences reduced. During the investigation of the serial killer, Jung-mon state that, based on his research, the killer always kill their victims during rainy days and have killed several other unknown victims as practice to kill more discreetly. Eventually, they manage to capture the serial killer who is a locksmith. However, they soon realize that the locksmith is not the only one and there are more serial killers like him who target women during rainy days. Eventually, Gu-tak makes a deal with the three convicts to work with the police to capture serial killers in exchange for reduced sentences until their sentences are reduced to zero, which all of them will be granted freedom. ==Cast==