4th Period Mystery
Movie| Title | 4교시 추리영역 |
| User score | 6.1 |
| Release date | Aug 12, 2009 |
| Genre | Crime, Mystery, Thriller, Action |
| Director | Sang-yong Lee |
| Production country | South Korea |
| Production companies | Sway Entertainment, Lotte Entertainment |
| Run time | 86 min. |
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.
