Ga-myeon plot
Detectives Kyung-yoon Cho and Eun-joo Park have been an inseparable duo since police academy. One day they are assigned a case of a stabbed to death owner of a sports center. The only clue they have is a hair with blood type AB. A swimming instructor is soon identified as the prime suspect, but is brutally murdered in the same way. It becomes known that the two victims committed a dishonorable act together with a third party in the army. The police see the murders as a serial murder case and as revenge for the victim. But as the identity of the culprit is gradually revealed, Detective Kyung-yoon stumbles upon another shocking mystery.