Catch the Ghost follows the story of the subway police squad as they attempt to protect the subway and its commuters from a notorious serial killer known as 'The Subway Ghost.' The narrative centers on Yoo Ryung, a passionate and impulsive rookie officer who joins the subway police force to find her missing autistic twin sister. She is partnered with Go Ji-seok, a rule-abiding and cautious veteran detective who prefers to follow protocol rather than take risks. As the duo navigates the complex underground labyrinth of the Seoul subway system, they uncover a web of corruption and hidden crimes. Their clashing personalities lead to constant friction, but they eventually form a strong bond as they work to solve the mystery behind the serial killer's identity. The series blends elements of procedural crime drama with lighthearted romantic comedy, highlighting the personal growth of the officers as they face their past traumas.