Su-yeol learns that K is closely linked to his childhood trauma. A girl shows up at the police station, delirious and covered in someone else's blood.

When bits of his memory return, Su-yeol reexamines the murder of his father. Finding similar cases, he learns one person was involved in all of them.

Su-yeol visits Shin Ju-hyeok to seek treatment, but unleashes a very angry K instead. A victim opens up after an attempted suicide.

Su-yeol's hunt for the truth endangers those around him. He has a final face-off with the crazed killer at the place where it all began.