Set against the backdrop of towering views of Mount Jiri, where rangers and other employees of the Jirisan National Park climb through the mysterious and unexplored regions of the mountain, trying to rescue the survivors and lost trekkers. Seo Yi Kang is the park's top ranger who has vast experience in navigation, making her knowledgeable when it comes to tracking down lost individuals. One day, she becomes the partner of Kang Hyun Jo, a rookie park ranger who is a military academy graduate and an ex-lieutenant who experienced a horrific incident on Mount Jiri which led him to become a ranger. The drama is centered around a mystery surrounding the mountain's many visitors; those who come to kill, and those who come to end their lives.