Season 1

Detective Taek-rok gets a prank call. The unknown caller says something he cannot ignore.

Taek-rok is framed for murder and gets interrogated. He delves into the past cases he undertook.

Taekrok realises the mistake he made in the past. The caller gives orders that cause Taekrok to become suspicious of everyone around him.

Taekrok entrusts the blackmailer's information to Jinhan then gets a clue about the blackmailer's identity.

Seong-a and Gyeong-chan decide to help Taek-rok, who realizes the blackmailer's target is not him.

Taek-rok chases a man who has a key to the truth. However, the man resists.