Xi Zhu (played by Shin Eun-kyung) witnessed the brutal murder of her father at the hands of the serial killer Ji Beom (played by Kim Sung-woo) when she was only seven years old. Despite many years having passed in the blink of an eye, the horrifying scenes and the wicked visage of the murderer continue to haunt Xi Zhu. Although Ji Beom was eventually brought to justice and imprisoned, it did little to quell the hatred that had taken root in Xi Zhu's heart. Fifteen years later, Ji Beom's sentence is served, and he regains his freedom, while Xi Zhu has grown up and embarked on her revenge plan; she is determined to take her father's revenge with her own hands. However, Ji Beom is inherently evil and cunning, and inexperienced Xi Zhu may end up failing in her quest for vengeance, potentially becoming another victim. Over the years, Detective Da Young (played by Yoon Jae-moon) has been looking after the orphaned Xi Zhu, and now, with similar serial murder cases occurring again, he too has begun a pursuit of the killer.