Hae-seong (Seo Kang-joon), an agent of the National Intelligence Service, becomes a high school student in order to find King Gojong's gold bars hidden in a hospital.

There is definitely something in the basement of the old building. In a situation where he has to go undercover again, Hae-sung is suspected of being a school bully by Soo-ah.

Haesung, who discovered the connection between gold bars and ghost stories, begins to investigate ghost stories at school.