Jang Yong-chul

Navigating both the criminal underworld and law enforcement agencies, professional snitches called "yadang" provide covert information about the drug world to prosecutors and police. When a drug bust at a party attended by high-profile second-generation VIPs entangles those involved into a dangerous conspiracy, a seasoned yadang must do everything in his power not just to make it out on top, but alive.

When two men find their lives derailed, they meet challenges that force them to face a fierce battle to protect their loved ones.

Major crimes unit detective Seong-jin arrests Tae-sung for petty crimes, but shocked to find out that he is the notorious serial killer. However, Seong-jin becomes doubtful of his identity as the serial murder case is investigated.