'Monster Cop' Ma Seok-do investigates an illegal online gambling business led by a former STS Baek and an IT genius CEO Chang. Ma proposes an unexpected alliance to Jang and begins hunting down the criminals.

A by-the-book police officer is assigned to secretly investigate a team leader who believes that the rules shouldn't stop an investigation. As the officer investigates further, his own attitudes begin to mirror the team leader's.

Jang-soo is a judo instructor who is indifferent to everyone but his daughter. One day he realizes he can see Tae-jin, a ghost who used to be a devoted police officer. Tae-jin asks Jang-soo to help solve the case that took his life away from him.

A young homeless man happens to draw a series of illustrations over dusty surfaces, gradually recovering from the pains of his past.