'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.
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.
During the Japanese colonial era, roughly 400 Korean people, who were forced onto Battleship Island 'Hashima Island' to mine for coal, attempt to escape.
Duk-soo lost his father and younger sister while taking refuge during the Korean War. He leaves for Germany to work as a miner and enters the Vietnam War. He wishes to find his sister.
A hitman accidentally kills a little girl. Filled with regret, he wants to quit. But then to tie up loose ends, he is forced to go on another job, to kill the girl's mother.