When a software developer creates a dating app that a serial killer uses to find his next targets, she’s drawn into a dark world of romance and murder.

Baek Ho-rang is a high school student. Due to her pretty appearance, she is popular on social media and at her school. Yet, Baek Ho-rang only has one friend, due to her condescending personality. Baek Ho-rang encounters a problem. She learns that someone is trying to unveil her secret. To find that anonymous person, Baek Ho-rang joins her high school's broadcasting club. Go Eun-taek is the chief of the broadcasting club. He is a perfectionist and respected by the club members.