By Episode 10, many of us here on this blog have already deduced that Kim Sol, the cultural anthropologist, is the serial killer.

To our theory, let me add a few points:

A. The trophies

The cave where YiKang and HyunJo hid from the bear is the place where the serial killer kept his “trophies” from his murders.

Kim Sol was probably in the cave because he was lamenting the loss of his memorabilia – or “murder”-abilia. The rangers had taken them away. To me, when Kim Sol put on his gloves as he left the cave, he was signaling his intention to “get down to business.” That is, he was serious about murdering again because his trophies were taken away.

B. What was HyunJo looking for?

Back in Episode 5, HyunJo mentioned to the Lottery Ticket girl that he was looking for something in the mountain. In this Episode, he also told Kim Sol that he was looking something.

HJ: I’m looking for something.
Sol: Did you lose something? The rangers already took all the lost articles near here.
HJ: What brings you here?
Sol: Here? This was my hideout when I was little. We called it the Black Bridge Valley Shelter.
HJ: Then…?
Sol: That’s right. This is my hometown.

That means that he and Private Lee knew each other because Private Lee was from this town, too.

HJ: Your hometown?
Sol: Yes. You’ve seen the video, right?
HJ: Yes.
Sol: What he said is all wrong. This village didn’t disappear because of cable cars or demolition. Villagers left because of the ghost lights.
HJ: What do you mean?
Sol: Whenever something bad happened to the village, the ghost lights always came first.
HJ: I heard wild beasts’ eyes glow like that reflected in the light when it’s dark. I saw them with my own eyes this time. The ones I saw were moon bears’ eyes.
Sol: Back then, there were no bears on the mountain. Whatever you’re looking for, I hope you find it.
HJ: Thanks.

I think that HyunJo was looking for an item that belonged to Private Kim Hyeonsu. When he and YiKang were stuck in the cave, he shone his flashlight on a ballchain. He was about to take a look at it when he spotted the injured hiker.

The ballchain had a dogtag which is a military ID.

The other items found in the cave were:

a running shoe,
a climbing rope with a frayed end,
a crampon, which is a gear attached to snow boots for mountain-climbing/,
a snake trap.

These items could be linked to the deaths that HyunJoo listed.

1. Sept 15, 2017. Pvt Kim Hyeonsu. Died in Baektogol during ruck march
2. Nov 16, 2017. Seo Geumja. Yangseokbong Peak, the rope broke
3. Jan 20, 2018. Lee Jonggu. Fell from Buam Cliff, Deokseoryeong
4. Mar 23m 2018. Kim Jindeok. Fell in Narigol Daeyeongri
5. Oct 10, 2018. (Granny) Lee Geum Rye. Baektogol. Bullet tree. Yogurt.
6. Oct ? 2018, (Snake poacher) Choi Il Man. Saemagol. Bomb.
7. Oct ? 2018. (Ranger) Lee Yang Sun. Saemagol. Bomb failed so tried to kill her with yogurt.
8. 2018. (Accomplice) SeWook. Killed in the pine tree habitat.
9. February 2019. Forest fire.

C. Who was Yang Geun Tak?

Yang Geun Tak was the missing hiker in Episode 1. When YiKang arrived at the Haedong base station after a year’s absence, Chief Jo was calling off the month-long search for him. The search was called “Yiseokjae incident” which happened on August 4, 2020. His body was found in the Gaeam Falls.

From Ep 9, we learned that he was in Jirisan in Spring 2019 to solicit support from the villagers for the construction of cable cars. Chief Jo alerted his colleague, the former Park Chief, that Yang Geun Tak was back, and the ex-Park Chief feared that the “mountain spirit would be enraged again.”

Park Chief: Are you determined to ruin the mountain? Why are you doing this?
Geun Tak: Ruin it? Jirisan is where I grew up. This is all for the mountain.
Park Chief: When the construction begins, the whole ecology will be destroyed. Is that for the mountain?
Geun Tak: Installing cable cars and blocking the trails are better for the environment. And not just for the environment. Nearby residents will benefit from it.
Park Chief: Black Bridge Village. Do you remember it? Have you forgotten? Have you forgotten all that’s happened there? I’ll never let that happen again. I will make it stop.

And then, we discover in Ep 10, that back in 1991, he had gone to the village to convince the mayor to sell and relocate their village so the cable cars could be built.

Young Kim Sol lost his parents because of Yang Geun Tak’s development plan.

D. What’s Kim Sol’s connection to Chief Jo?

Back in 1991, Chief Jo promised Kim Sol’s dad that he would protect their village with all his might. Kim Sol’s dad was the mayor of Black Bridge Village.

But he was failed to rescue Kim Sol’s mom in time to save her. Young Kim Sol overheard Chief Jo blaming himself.

Chief Jo: It’s all because of me. I heard that she could have survived if we were a little quicker. I passed by that tree several times. Had I found her a little earlier…
Ex-Park Chief: Let’s go in. We should see her off.

After Kim Sol’s mother died, his father fell into a depression, and committed suicide. Chief Jo would feel responsible for the little boy. I wouldn’t be surprised if Chief Jo had a gut feeling that Kim Sol was behind the serial murders, and was doing his best to search for the yogurt bottles and yellow ribbons that Kim Sol left behind. Chief Jo hid the yogurt behind his back when he met Ranger Lee Dawon in the forest to avoid arousing her suspicion. Unfortunately, however, his guilty demeanor only made Dawon suspect him even more. She failed to consider that Chief Jo had no motive to kill Granny or Ranger Lee Yansun, and she relaxed her guard when she met the actual killer.

That’s it for now.