In Chinatown, law and order is turned upside down when a trio of feral Chinese gangsters arrive, start terrorizing civilians, and usurping territory. The beleaguered local gangsters team up with the police, lead by the badass loose cannon Ma Seok-do, to bring them down. Based on a true story.

The 'Beast Cop' Ma Seok-do heads to a foreign country to extradite a suspect, but soon after his arrival, he discovers additional murder cases and hears about a vicious killer who has been committing crimes against tourists for several years.

Detective Ma Seok-do changes his affiliation from the Geumcheon Police Station to the Metropolitan Investigation Team, in order to eradicate Japanese gangsters who enter Korea to commit heinous crimes.

'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.