Cha Soo-Yeol, a dedicated police officer, has spent his life consumed by hatred for his mother, Jeong I-Shin—the notorious serial killer known as "The Mantis." Twenty years ago, she brutally murdered five men, and the scars of her crimes have haunted him ever since. But when a new wave of grisly murders, eerily similar to her killings, surfaces, Soo-Yeol is forced into a reluctant partnership with the very woman he despises. To stop the copycat killer, he must rely on the twisted mind that created the original carnage. As Soo-Yeol grapples with his hatred and the tension of working with his mother, he is pushed to confront his dark past. Together, they uncover unsettling truths, blurring the lines between justice, vengeance, and the disturbing bond between mother and son in this gripping thriller.