Yi Xing and Xiao Jiao disappeared on the day one of their friends held a party on an island. Their grandmother had a haunting dream of the twins begging for her to find their bodies before they disappear forever. A year later, their cousin Ming En arranges for a search team consisting of their friends to help find a sign of the twins’ survival.

The story is set in a high school, where an elite group of 32 students — including Kim Tanny, her younger sister Kim Minhae and their group Dark Angels and some group of guys called Teentop , Infinite , BAP and Boyfriend — are taking a special class for their college entrance exam. Suddenly....a disembodied voice announces that their life depends on the exam questions He/She/They will set for them, and that a student will die for ev