"The Clue (2009)"

During fourth period, high schooler Da-jeong finds his 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.
Downloads :

http://www.indowebster.com/4th_Period_Mysteryavi.html

English Subtitle :

http://www.indowebster.com/4th_Period_Mysterysrt.html