In an all-boys school, a class of 12th grade students are in disbelief after doing a seance that revealed the presence of a ghost lurking among them. Soon their doubt turns into suspicion as the class runs into eerie events that compel them to deduce the ghost's identity.
In a late-night seance, the students of Grade 12 - Class 4 in Boseok Boys' High School discover the possibility of a ghost haunting their classroom. Their homeroom teacher coincidentally falls unconscious in the stairwell.
Ye-dam's music demo gets tampered with an eerie paranormal noise. Hyun-suk carries out his ghost-hunting tactics and notices something weird about Asahi.
Asahi disproves his classmates' suspicions about him. Jung-hwan films a ghost-hunting vlog inside their classroom, much to Do-young's anxiety. Jae-hyuk obtains an anti-ghost talisman, its magic unexpectedly working against Haruto.
Desperate to satisfy his online followers, Jung-hwan resorts to secretly fabricating fake paranormal events and filming his classmates' reactions to them. Jae-hyuk unexpectedly discovers the ghost's identity.
Yoshinori discovers Haruto's identity through tarot card reading. At the spring festival, Class 4 fails to scare their customers in their haunted house booth. Haruto decides to step in, but things quickly turn awry.
Jeong-woo is hospitalized after the school-wide paranormal event at the spring festival. Class 4 finds itself pointing fingers at each other. Do-young discovers the ghost's identity and Haruto is forced to explain himself.
Haruto reveals his sad tale to the students of Class 4. Do-young becomes resentful of Haruto after failing to obtain Mr. Ha's recommendation letter. In shock, Mr. Ha finally realizes Haruto's identity.
After confronting Haruto in fit of rage, Mr. Ha threatens to impose penalties on anyone who interacts with the ghost. Yoshinori's grandmother holds a classroom exorcism, putting Class 4's sympathy for Haruto to the test.
