Jungkook, the unconvicted killer of the Busan Serial Murders, has spent the last three years in a mental hospital, awaiting his release. When he is set free, his plans to begin another murder spree are halted by the presence of Kim Namjoon, a watchful and suspicious police chief. Jungkook gets a job at Namjoon's husband's coffee shop and meets Yoongi, a quiet, grumpy artist. Jungkook settles on Yoongi as his next victim, but as he follows the artist, he starts to feel something new…when a rival killer targets Yoongi, can Jungkook save him in time?