Jung Yi-Shin (Ko Hyun-Jung) is a serial killer with the nickname of the Mantis. She brutally murdered 5 men 20 years ago. Her son is Cha Soo-Yeol (Jang Dong-Yoon). He has loathed his mother for his entire life. He now works as a police officer. One day, a murder case takes place. The murder seems to be a copycat crime copied from Mantis. To catch this culprit, Cha Soo-Yeol enlists the help of his mother Jung Yi-Shin.
