The mystery drama is about park rangers who work to rescue people at Mount Jiri. Jun Ji Hyun will play Seo Yi Kang, the top ranger who knows everything about navigating Mount Jiri National Park. Joo Ji Hoon’s character Kang Hyun Jo is a military academy graduate with a deep secret who joins as a new ranger and becomes Seo Yi Kang’s partner. Jung Goo Young is an extremely practical ranger who believes that the key to saving others is saving himself first. He leaves his job right on the clock, regularly takes vacation days, and disappears almost before he can be dismissed. Jo Dae Jin, the head of the Haedong Branch Office in Mount Jiri National Park, is called “Mount Jiri Man” because he has been a ranger for half his life. He is a simple, honest man who is fully committed to his job and takes responsibility for his junior rangers.