Hyung Min is asked to head a special investigation unit to take down an organized crime kingpin.

Complications occur when Shi Hyun, known as the Doctor's Son, takes control of Scale's operation.

Kyung Mi runs into trouble while undercover as Eun Soo tries to infiltrate the kingpin's drug ring.

Hyung Min convinces Soo Min to go undercover to track down the drug lord called the Doctor's Son.

Hyung Min finds out that one of his police colleagues is actually a crime syndicate spy.

Vice chief Kang's spy Seo Yungyeong is exposed, and Kang plans to kill Yungyeong as he fears she will reveal his identity.