Jeong Soo-na (Go Eun-ah) is a 17-year-old high school student who lives with her uncle, Se-jin (Jeong Yu-seok), and grandmother (Jeong Yeong-sook) in a big mansion. Her bullied best friend, Lee Han-jeong (Lee Da-in) is subjected to a cruel prank that humiliates her at a public place that she decides to commit suicide by jumping on the railway. She returns home, but becomes a hikikomori (a reclusive lifestyle) until her bully arrives to apologize, only to find Han-jeong's dead body littered with splattered blood and vermin. The news drives Soo-na over the edge, while Han-jeong's bully commits suicide by jumping from the rooftop because of her trauma.