I let out an “um,” and immediately sensed that something was off. Listening more closely, it increasingly felt like it wasn’t just talking; I couldn’t be sure it was laughter, but it was very similar. The others also noticed it. Anning stopped calling, and we exchanged glances, all a bit surprised.

The team doctor asked, “What’s going on? Are they… laughing? Did they hear our voices and get too happy?”

Zaxi countered, “Is that how you laugh when you’re happy?”

Anning looked puzzled as well. She stopped calling and continued adjusting the intercom, trying to make the sounds inside clearer. The adjustments didn’t help much, but the sound did become a bit louder. We pressed our ears against it again and could hear it more distinctly; it really sounded like a cold, sinister laugh, so full of malice that it didn’t seem like it came from a normal person—it was more like the laughter of someone from a lunatic asylum. However, upon careful listening, I felt that there were some other very faint sounds mixed in with the laughter. The two types of sounds blended together, creating an eerie atmosphere in this terrifying devil’s city.

Listening to this malicious cold laugh made me feel very uncomfortable. Even Zaxi, who had been acting all smug on the way here, now looked scared, his face pale as he swallowed hard and said, “What the hell, that laugh sounds really awful.”

Anning gestured for him to be quiet, pressed the intercom to her ear, and listened for a while before saying, “This doesn’t sound like a human voice!”

“Don’t say nonsense!” the team doctor exclaimed. “If it’s not human, then is it a ghost?”

“Listen carefully,” Anning urged us to lean in. “The frequency of this sound is very fast, and the pitch is almost flat. It’s been going on for five minutes; can you try laughing like that for five minutes?”

I thought about it and felt she had a point, so I asked, “Then what is this sound?”

“This frequency should be mechanical, like a watch pressed against the intercom. But since the frequency isn’t fixed, it could also be someone continuously scraping their nails against the intercom’s microphone,” Anning demonstrated. “Combined with static noise, it results in this sound.”

“Scraping their nails on the intercom? Why would they do that?” the team doctor asked. “Why not shout? Maybe we could hear them without the intercom.”

As soon as he said that, both Zaxi and Anning’s expressions changed, and I suddenly realized something: “They might be in a situation where they can’t shout or speak, and can only communicate with us this way.”

“The quicksand pit! They must be stuck in a quicksand pit!” Zaxi exclaimed. “They might have sunk down to just their heads; in that case, even a fart would make them sink!”

“Damn it!” We all tensed up immediately, standing up to look around in the darkness, wondering where it could be.

Anning maintained a fair amount of calm. She clapped her hands to keep us from panicking. “Calm down, calm down. The fact that they can send a signal means they are temporarily safe. The fact that we can receive the signal indicates that their intercom must be nearby; we should be able to reach them soon.”

“But saying it’s nearby, this area is still very large. How do we find them?”

Anning instructed us to follow her and began walking around with the intercom, trying to determine the direction from which the signal was coming.

As soon as I realized it, I thought, how could I have not considered this? Even though I consider myself knowledgeable, in this kind of terrain, to receive radio signals, there must be gaps in the surrounding terrain that allow for the diffraction of radio waves. Moreover, the degree of radio signal attenuation is closely related to distance, so by assessing the reception of radio waves through the walkie-talkie, we could determine whether we were getting closer.

We immediately followed, and after walking around for a bit, we found that the signal was strongest deep within the canyon, indicating that the source of the signal was inside the canyon. An Ning called out, and we quickly ran inside, while the flashlight was already swinging to illuminate the path. Zaxi shouted, “Watch your step, don’t just look around!”

We couldn’t worry about that anymore; we ran and searched at the same time. Soon, we reached the end of the canyon, where a massive crescent-shaped mound blocked our way. It was about fifty meters high, resembling a giant sail, very steep, and it looked impossible to climb over.

Anyone familiar with walkie-talkies would know the situation immediately. In such terrain, radio signals would be at their weakest, similar to poor signals in mountain valleys. However, when we looked at the walkie-talkie, the sound was now very clear and had not weakened at all. This meant that the source of the signal was definitely within the area enclosed by this crescent-shaped mound, which measured about one hundred and ten meters in length and width.

“Right here?” We all broke into a cold sweat, sensing something was off because when the flashlight swept across, the area was completely visible, and there wasn’t even a ghostly shadow.

“Could they have already sunk down?” A bad thought crossed my mind.

An Ning shook her head because the sound from the walkie-talkie was still ringing out, and she called for us to spread out and search.

We dispersed and carefully searched for traces on the ground. Soon, Zaxi shouted out that he had made a discovery. We rushed over and found very chaotic footprints on the ground. They weren’t ours.

“They were right here,” Zaxi said. “This crescent-shaped mound is like a windbreak; they must have been forced in here to take shelter from the fierce wind, and there is almost no wind inside, which is why the footprints were left behind.”

We immediately followed the footprints forward. The sandy ground showed very clear footprints, indicating three people. We followed the footprints for more than ten meters until we reached the base of the mound, where the footprints suddenly stopped. There were no footprints turning or any signs of quicksand.

“Damn. Did they go inside the mound?” Zaxi clicked his tongue.

“No!” An Ning showed an incredulous expression. She looked up at the mound, which was completely dark, and nothing could be seen. “They climbed up.”

This was strange; we all froze and looked up. The backlit mound was a solid black, like a massive black curtain. Our flashlight beam swept up, but it was so high that the small beam of light couldn’t reveal the whole picture.

What could they be doing up there? Was there something on top of the mound?

At that moment, An Ning told us to step back, then took out a signal flare and shot it into the sky.

The blazing signal flare shot up into the air and exploded, illuminating the entire area as bright as day. In that instant, everything hidden in the shadows around us became visible.

We all turned our eyes to the surroundings, and the sudden brightness made it a bit uncomfortable for our eyes. Before we could see clearly, we heard An Ning exclaim, “Oh my gosh!” We squinted and looked up towards the sky, and in the shimmering light of the signal flare, we saw a massive object embedded in the hillside of a huge crescent-shaped hill. Half of it was buried in the earth, while the other half jutted out abruptly into the air.