4th Period Mystery (2009)
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.
- Country : South Korea
- Genre : Crime, Mystery, Thriller, Action
- Studio : Sway Entertainment, Lotte Entertainment
- Director : Sang-yong Lee
- Cast : Yoo Seung-ho, Kang So-ra, Sang-geun Jo, Jeong Seok-yong, Jeon Jun-hong, Lee Yeong-jin