Queen Mantis

When a series of terrible murders ensues in a residential area, Cha Su-yeol is forced to seek help from Jeong I-sin, a serial killer from the past.

I-shin offers assistance with the investigation, but its unclear why she would help a cop. Su-yeol unravels the origins of I-shins murderous instinct.

Su-yeol finds I-shin in his home after she vanishes under police watch. The killer demands to speak to I-shin and gives her a hint about the plan.

As Jung-yeon copes with the truth of Su-yeols past, the killer reveals their identity — and takes a hostage, forcing Su-yeol into a dangerous bargain.