Nestled deep in the mountains, the prestigious Susin High School only accepts the top 0.1% of student applicants. It gained prominence for a year-long program that teaches students how to study and is known as one of the best schools to attend for getting into a good college both in Korea and abroad. The students’ only vacation during the year—an eight-day break during winter—is about to start. Everyone is excited about leaving the school, except for seven students who received mysterious, anonymous letters. They will remain at school over the holiday, together with a single teacher on watch duty. After getting into a car accident, psychiatrist Kim Yohan discovers the high school, asks for assistance, then ultimately ends up staying there. A record-breaking blizzard sweeps through, cutting the school off from the outside world. The seven students begin searching for the anonymous sender of the letters, in the process of which their individual personalities come to light, organic relationships are formed, and they ultimately come face to face with reality.