Drama Special Series Season 1: White Christmas

After receiving an anonymous letter stating that someone would die, eight students at the elite boarding school, Susin High School, nicknamed "Prison High", decided to remain at school for the 8 days of winter break. To accompany them, a teacher is forced to remain.
On their first night, a psychologist named Kim Yo Han takes refuge at the school after being involved in a car accident nearby. Due to the snowstorm, the roads are closed, and he is forced to spend the winter holiday with them. However, at a time when everyone else is celebrating Christmas Eve, the students realize that the anonymous letters they each received were not the result of a harmless prank; and that there is a murderer in their midst.