During fourth period, high schooler Da-jeong finds her classmate Tae-gyu dead in a classroom and Jeong-hun standing in front of him with blood on his clothes. In order to stop Jeong-hun from becoming the prime suspect, Da-jeong must help him find the real murderer, who is still inside the school building, under 40 minutes before period four ends.
as Han Jung-hoon
as Lee Da-jeong
as Kim Tae-gyoo
as Kang Gook-man
as Embassy
as Yun Sang-mi
as Do-il
as Hong Ju-hee
as Crazy
as Student in grade 2 class 5
as Virtual Criminal
