Strange rumors start to spread at the catholic girls' high school after Eon-joo committs suicide one night. Eon-joo's younger sister Jeong-eon who attends the same school, has suspicions about Eon-joo's death. After persistent investigation, Jeong-eon finds out that on the night of the incident, Soy, Yoo-jin, Eun-yeong and Eon-joo had tried to commit a joint suicide after making a blood pledge--but the other three girls are still alive. The desire, jealousy and lies behind the vow of death between the four girls is revealed, along with the hidden truth behind Eon-joo's suicide.