After the back wall of the cupboard was fully opened, Qiuzhen found that behind the cupboard was another cupboard. The cupboard behind the cupboard was similar to a closet. So, Qiuzhen stood in front of a small room that seemed to function as a closet. If there was no cupboard in front of the closet, then the room would be just a niche in the wall. Qiuzhen, who had been convinced that there was a secret passage behind the cupboard, was a little disappointed. He lay in the closet because he felt a little tired after a while of fiddling with the lever to open it.

The more he thought, the more confused he became. He thought about the reason why people made a closet like that if it would only be covered by a cupboard. And, it was also not easy to open it. All of that seemed unreasonable. The existence of another way out behind the closet was a much more plausible thing. But, unlike the cupboard wall in front of the niche, the wall behind was a solid wall.

Qiuzhen lay on his back with his head on the left side of the closet. The width of the closet was about one and a half meters. He had to bend his legs so he could lie in the closet. Because he had struggled to get to that place, Qiuzhen was reluctant to return to the subway station straight away. He decided to rest while lying down for a while.

He idly kicked the surface of the wall at his feet. Unlike the closet's back wall, Choujin felt something different from the wall on the left. There were certain parts of the wall that he felt were not solid. Qiuzhen stopped kicking. He got up to start checking at once.

Qiuzhen discovered that some parts of the walls were not made of concrete. With her fingers, Qiuzhen felt more thoroughly on the surface of that part of the wall. Unlike the wall of the cupboard in front of him, which was made of wood, the part that Qiuzhen found was made of some kind of metal. Qiuzhen didn't know what kind of metal it was because when he touched the wall, he didn't feel like he was touching iron, But Qiuzhen was sure that the part wasn't made of wood. The problem was that the passage was so small that he doubted it was the entrance to a secret passage.

When Qiuzhen looked more closely using the flashlight, he realized that this passage was indeed similar to an entrance. But not an entrance for humans, more like a dog or cat entrance. In Qiuzhen's hometown, this kind of entrance was called the Dog Door. So-called because it was the entrance for dogs. For cats, this kind of entrance was called the Cat Door. The difference was in terms of size. The Dog Door was much bigger than the Cat Door.

Qiuzhen thought for a moment. A fairly large dog could indeed pass the entrance. A child would definitely be able to break through. But an adult, like himself, Qiuzhen, was a bit hesitant. If he forced himself, he was afraid he would get stuck in the door. No one knew he was there. Qiuzhen realized he was facing a pretty enormous risk. But he had to make a quick decision.

If I got stuck and couldn't get out, wouldn't I suffer for several days before finally dying of hunger and thirst?

Qiuzhen laughed to himself at the thought of that. It's ironic, so many things he had experienced and yet he must die stuck in a Dog Door.

As he continued to stare at the passage, he kept thinking about how to open it. He looked for something that resembled a lever, but he couldn't find it. It occurred to him to look for objects made of metal to break down the surface of the Dog Door. But he was still patient. Using such violence was a last resort. Qiuzhen then used his flashlight to illuminate the entire corner of the closet once again.

Then he turned around. He also highlighted where he had come from earlier. He looked again at the two levers in the cupboard. Suddenly, Qiuzhen realized that there was a part he had not noticed, namely the back wall of the cupboard that he had moved to the side. He had already seen from the front when he opened the cupboard. But he didn't see the other side because he had already moved to the side when he found the closet.

Now he was in the closet. So he had to shift back the part that insulated the closet with the cupboard in front of him. Qiuzhen stood up and began to grope the wall. Just before shifting the wall, Qiuzhen gave up his intention. He didn't know how to open the sliding wall from the inside. It wouldn't be funny at all if he got stuck there because he didn't know how to open the wall. Qiuzhen then moved the wooden wall but did not completely cover the back of the cupboard. Only cover half of it. After that, he checked every inch of the wall.

Finally, he found something at the top of the wall. There were three buttons on the top. For a moment, he hesitated again, but in the end, he had the courage to move the wall completely so that the closet where he was standing was tightly closed. Just as the wall closed completely, Qiuzhen heard a "click." He was certain that it was an automatic lock mechanism.

To open the wall from the outside was to first press the combination of buttons on the two levers before moving the two levers. In order to open it from the inside, Qiuzhen tried to push the buttons at the top of the wall one by one. After trying several times, he finally succeeded. Turned out he had to press each button three times. After a "click" sound came from the device, he could move the wall so that the barrier between the closet and the cupboard was wide open.

Qiuzhen shifted the wall again. After closing it completely, he observed the wall's surface from the inside. Unlike the outer side, which was the inner side of the cupboard, the inner side of this wall was not plain.

There was a painting there. The picture was painted on the surface of the wooden wall. Indeed, the image had faded, maybe because it had been so long. The object in the painting was an endless wall. The long wall was depicted snaking like a snake. Qiuzhen guessed that the long wall was the legendary long wall that existed in the old world where their ancestors lived thousands of years ago.

The old world where their ancestors came from was not homogeneous. There were various cultures and civilizations there. During the great migration, all the countries sent their inhabitants into space on giant colony spaceships. According to the history that Qiuzhen learned at school, there were about a hundred fleets departing from the old world. Each fleet comprised hundreds of colony spaceships.

Not everyone was willing to leave the old world. What would happen to the people who chose to stay there?

One of the important regions or countries in the old world was the place where the ancestors of Qiuzhen and many other people came from. In that area, a legendary wall was an essential part of the history of their ancestral civilization. The wall was built long before the great migration. Even the first construction of a section of the wall took place over two thousand years before the people there left their planet.

Unlike Zhengyi or Shanquan, who were very fond of studying things related to the old world, Qiuzhen, like most people in the new world, knew very little about the history of their ancestral civilization in the old world. So he couldn't remember any more information. The painting aroused curiosity in Qiuzhen. He promised himself not to forget to ask Shanquan or Zhengyi about it when he got home. Qiuzhen hoped he would make it through the night without encountering more difficulties than he had been through.

But the painting had nothing to do with how to open the Dog Door. So it was clear that no matter how much information Qiuzhen remembered, it wouldn't make things any better.

Qiuzhen lay down again inside the closet. He kicked the Dog Door again. But this time, he felt something different from the part of the wall he kicked. He quickly got up and looked at the Dog Door again. The plate now looked nothing like before. Qiuzhen felt the entire surface of the plate. When his hand pulled the bottom of the plate, it turned out that he could open it. The Dog's door could open easily. The plate opened towards him. So it's like when people open the hood of a car. It turned out that there were conditions to open the Dog Door. The first was that the closet must be closed. And the second was that the plate must be pulled, not pushed.

Qiuzhen again cheered with joy. He pulled the plate so that the Dog Door was fully open. Once he reached that stage, he couldn't back down anymore. Qiuzhen should try to get into the room behind the Dog Door. The burning curiosity overcame the fear that overtook Qiuzhen.

Cautiously, he began to curl up. It was the only way to enter the door. Slowly but surely, Qiuzhen shifted his body forward. Little by little, he entered through the door. Crawling like a snake was not a simple thing. But Qiuzhen enjoyed it. He couldn't explain the exact reason behind the feeling. Perhaps the satisfaction of having managed to enter the door had made Qiuzhen's subconscious feel a distinct impression.

The thing that probably made it a little difficult for him to get through the Dog Door was the fact that he was full. Just before Qiuzhen embarked on such a perilous journey, he had already eaten quite a bit of food. A bulging stomach automatically made it difficult for him to move faster. But that didn't dampen Qiuzhen's spirit. He inched patiently. Inch by inch, his body crept away under the Dog Door.

Finally, Qiuzhen passed through the door. The Dog's door automatically closed after its whole body penetrated the door. He found himself in another room. Before starting to explore the space, Qiuzhen turned around to examine the door he had just entered. He had to know how to open the door to avoid wasting time thinking when he had to leave. It turned out that his worries were unfounded. From inside the room, the Dog Door was effortless to open. All he had to do was push the door open. After feeling relieved, Qiuzhen then stood up. He was ready to inspect the room.

Qiuzhen was in a rectangular room. At least that's the impression Qiuzhen got from the room. Except for the Dog Door where he had come earlier, the entire wall of the room was covered with piles of stuff. The situation was almost the same as the three rooms that Qiuzhen had found earlier. The difference was that the room was much smaller. With the help of the light that came out of his flashlight, Qiuzhen explored all corners of the room. He was sure that another door was here. According to his guess, the door must be hidden behind the pile of things there.