Season 1
Seo Yigang is the best ranger at Jirisan National Park. She knows virtually everything about the area, including where to climb the mountain. Kang Hyeonjo is a rookie ranger at Jirisan National Park. He graduated from the military academy and was once an army captain. He has a secret that he can't tell anyone about. These two people become partners and they work to save people around Jirisan National Park.
Episode 1
Newly recruited park ranger Kang Hyeonjo is sent to search for a teen who has gone missing in Jirisan National Park but is impeded by a typhoon.
Episode 2
While pursuing a vision on the mountain, Hyeonjo meets a man who's searching for his father’s ashes. The two continue their risky ascent together.
Episode 3
The rangers stop a shamanic ceremony, and a girl passes a mysterious message to Hyeonjo. The team gets a report that an elderly woman has disappeared.
Episode 4
Seo Yigang beholds a spooky scene in a video recording. Back in 2018, the team is unfairly blamed for the death of a villager.
Episode 5
Yigang tells Hyeonjo that she saw someone with scratch marks on their hand. He suspects it may be the bomber. The rangers look for Lee Yangseon.
Episode 6
Snow closes the park. Yigang learns that someone with the same name as her first love is coming to collect an item. A suspicious car approaches.
Episode 7
Yigang realizes that Hyeonjo’s soul is wandering the mountain. In 2019, Hyeonjo sees a vision of a fire. The two are in danger in different places.
Episode 8
Following a rescue attempt, Hyeonjo finds out that someone has been trying to kill him and realizes that the recent murders weren't a coincidence.
Episode 9
Lee Dawon is missing. The rangers go in search and find Dawon’s phone, which contains a suspicious voice recording with an unexpected person.
Episode 10
The police find a man lying in shock in the road. Yigang and Hyeonjo get lost on their way to a village and see ominous lights in the darkness.
Episode 11
Cho Daejin is arrested as a suspect in Dawon’s death. Yigang develops a strong hunch that one of the rangers is actually the killer.
Episode 12
The rangers search for groups of climbers trapped in the park by heavy rainfall. Yigang meets a survivor of the 1995 flood that killed her parents.
Episode 13
The rainfall causes fatalities. Hyeonjo discovers that the accident on the bridge was intentional and looks into the connections between the victims.
Episode 14
At Geomeundarigol Village, Hyeonjo catches a suspicious man in black gloves. After hearing his testimony, Hyeonjo starts to suspect someone new.
Episode 15
Hyeonjo’s family decides to switch off his life support. The rangers start looking into people connected to the village, and Yigang has a revelation.
Episode 16
After the truth is finally revealed, Yigang grills the perpetrator. The culprit goes to conceal some evidence, but there meets Hyeonjo’s soul.