Se-hee is haunted by her step sister Tae-yeon who used to be a promising swimmer but suddenly killed herself in a swimming pool 2 years ago. During the summer vacation, she joins the study camp with 30 other elite students. On the first night, she sees a dead girl's body hanging upside down. Subsequently, a succession of cruel killings occurs whenever the group fails to answer a given question in time. Meanwhile, the hidden truth behind Tae-yeon's suicide is slowly revealed a...more

Se-hee is haunted by her step sister Tae-yeon who used to be a promising swimmer but suddenly killed herself in a swimming pool 2 years ago. During the summer vacation, she joins the study camp with 30 other elite students. On the first night, she sees a dead girl's body hanging upside down. Subsequently, a succession of cruel killings occurs whenever the group fails to answer a given question in time. Meanwhile, the hidden truth behind Tae-yeon's suicide is slowly revealed and terrified students struggle to undo the puzzle before they become the next victim.
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