21-year-old Ryu Yeon-seong is about to start his mandatory military service in the ROK Army. But unlike most other conscripts, he and four others are assigned to the mountain police rescue unit stationed at Mt. Bukhan, a small mountain on the outskirts of Seoul. Not knowing much about it, they think it'll be a walk in the park, and count themselves lucky to have landed such a cushy assignment. But when they arrive at the mountain, the group soon learn that they're in for more than they bargained for.