Half leaning against the stone wall, I carefully observed the cave, which was sloping downward. There are square grooves in each stone wall at a certain distance, as if something had been placed before that.

The old man at the front had already begun to move, and several of us followed closely behind, and because the hole was inclined downwards and very steep, we did not dare to go too fast, and tried to control the center of gravity of our bodies to prevent them from rolling down.

I walked at the rear, holding my breath, not daring to go too fast, and followed closely behind the camel.

At that moment, I heard a rustling sound in my ears, and it sounded like it was coming from behind me. I stopped, and listened carefully, but I didn't hear anything.

When I walked again, I heard another rustling sound, and the sound was getting closer and closer to me. I turned my head sharply, and saw that there was a secret door on the top of the cave that was not very large, and a large pale hand suddenly stretched out from it and pushed it violently on my shoulder. I secretly screamed that it was not good, because the whole center of gravity was in the back, and now I was pushed by the big hand, and the whole person began to fall backwards.

Before the camel in front of me could understand what was going on, it flew forward, and like a domino effect, we all rolled uncontrollably down the hole.

Boom!

I was sure that I was lying on someone, raised my head, looked at Zhang Yu, and hurriedly got up embarrassed. It was dim all around, and the old man had already stood up and walked to the side, and there was a sound of "popping" under his feet. I picked up the flashlight and took a look, and there were bones all over the ground, and there was a lot of sand, and the hole we rolled down was more than ten meters above the ground, and if it weren't for the sand, it would be really life-threatening.

The old man walked to the side, and in front of the old man was an exit, which could also be said to be the entrance to the entrance, but now it was sealed by a huge cobblestone, which must have been sealed a long time ago.

We gathered the lights and looked around. After about half an hour, we learned that this was a morgue and that the hole in it had been brought in by the corpses. The whole hole is funnel-shaped, thick at the top and thin at the bottom.

However, there are a few places that make us full of doubts, the first is that there are slots in the entire stone wall, and the so-called slots are a crack about half a meter long. At intervals of more than half a meter, there is a slot, which can be seen by the light of a flashlight, which extends all the way to the top of the cave. Unfortunately, only a stone slab remains in the slot on the right side of the roof of the cave. The slate looks very thin, but it is very hard. And on top of it is a black round bottle, about ten meters high, with a radius of about five decimeters. Leaning against the round bottle, there is also a pair of pulp. I didn't see a boat, let alone a river, and there was an extra pair of pulp for no reason, which was really incomprehensible. The second question is why there is sand for no reason with the extra sand under our feet, and how does the sand come from?

Our group began to ponder. The old man took out a cigarette and smoked it, and from time to time he pointed his flashlight above the roof of the cave. But the distance of the flashlight is limited, and the top of the cave is blurry, and the roof of the cave is not visible at all.

Seeing this, my uncle snuffed out his cigarette butt and waved his hand at Zhang Yu and me. As soon as I passed, my uncle immediately opened the toolbox, took out the telescopic ladder, and put it on the wall, "Zhang Yu, you climb to the entrance of the cave and see what kind of mechanism is on it, Xiao Ke, you follow behind Zhang Yu and try to cooperate with Zhang Yu."

Zhang Yu and I nodded, with a flashlight on each of our waists, and began to walk up the ladder along the top of the hole.

When Zhang Yu and I arrived at the top of the cave, we were all on one side, shining a flashlight into the sky, and it was pitch black. Or because of the distance, Zhang Yu and I don't know how high the top of the cave is, but it is far beyond the range of the flashlight.

The uncle below began to shout at us, asking if we had any discoveries, and I was about to speak, Zhang Yu made a silent gesture to me, and he replied loudly: "Wait, give me a little time."

Zhang Yu did not give up and used the flashlight to shine on the surroundings again, but I didn't want to do it again, in vain, sitting on the ground, my eyes couldn't help but glance towards the hole when I came before.

I suddenly remembered the big hand from before, and a trace of sweat couldn't help but overflow on my back.

Then I had a flash of inspiration, slapped my thigh, and said loudly, "Yes." Zhang Yu, I have made a new discovery."

It turned out that when I was glancing into the cave just now, I suddenly heard the secret door. There is a secret door, and there must be a road above the secret door, that is, the path that the mysterious man walked is above the hole, that is, above our heads. And we are standing at the entrance of the cave, focusing on the front, to the left, and to the right, and ignoring the top of our heads.

Now we can assume that the diameter of the hole is r, and we stay on this diameter, and let us be a segment of the microelement on the diameter, which is dx. There is also a distance above the entrance that we can see with the naked eye and by light. The stone wall is in a straight line with us. If there is a barrel on each side of the line, we can only see the line and beyond the line due to the blind spot, and we cannot see the inside of the line, so we can only see one barrel. That is, if there is a groove in the stone wall above us, there is a path in it that we cannot see at all.

Zhang Yu listened to my inference, hurriedly put down the bag on his body, threw it at my feet, dressed lightly, and said with a solemn face: "According to what you said, there is a road above this hole, and it is very likely to be a circular road, and it is superimposed, layer by layer, connected by stone steps. Because of this, we can't get light because of the distance." After saying that, he half-squatted down.

I was stunned for a moment, Zhang Yu's eyes motioned for me to step on his shoulder, looking at the black top, it was very clear which distance point had a groove. I took a sharp breath and jumped, my body like a lion rushing out, very fast. My hands grabbed at the stone wall, and sure enough, when my hand hung in the air for a while, and when it fell, it pressed to a flat ground. I was overjoyed, and I hurriedly gathered all my strength and crawled upward.

After reaching the top, I stretched out my hand, but found that the top of the cave was more than two meters high from me, and Zhang Yu couldn't get up. Thinking of this, I shouted to Zhang Yu: "You and Uncle Tell them that there is a new discovery, let them wait." Zhang Yu, you throw the flashlight at me."

Taking the flashlight, I began to stand up, and by the dim light of the flashlight, I could only see the road ahead, as I had thought before, in a circle, and less than ten meters away from me, there was a step. As Zhang Yu said, this road is made of overlaps.

Before I could reach the stairs, I saw a hollow square with a secret gray door in it. The secret door had been opened, and I looked around, and I didn't dare to come out, and the mysterious man didn't know if he was hiding around.

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