Summer House Murder

Geonhee and his friends visit his father's summer house. During the preparations for a campfire Ji-ah disappears, and Yejun discovers her unconscious. The friends panic as she drools blood. Geonhee calmly checks everyone's alibi and finds Yumi to be a suspect, to which she denies. Locking Yumi in an isolation room, they each look for clues. What is the truth, and who's deed could it have been?