Ma Seok-do, a police officer, goes to a foreign country to extradite a suspect but stumbles upon additional murder cases. He soon discovers a terrifying killer named Kang Hae-sang who has been targeting tourists for years. With his team, Ma embarks on an intense investigation that spans two countries, following the trail left behind by Kang. No borders will stop them from catching the criminal.

'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.

In Seoul, South Korea, a detective is determined to take down an organized crime gang. With the help of his team, he goes on a relentless pursuit to bring justice to the city. As tensions rise and alliances are tested, the detective must navigate through a web of corruption and danger to bring the criminals to justice.

Seven years after the roundup in Vietnam, detective Ma Seok-do joins a new squad to investigate a murder case. As he delves deeper into the case, he discovers a connection to a synthetic drug and a dangerous gang of thugs.