After listening to You Longfei's words, Zhang Mengde and Wu Er both fell into deep thought, it was indeed the first time they heard such a strange news, but Song Pan scratched his head: "It's not me who said it, you kid is the stepmother who has corrupted the social atmosphere is all crooked, besides, isn't it too reckless to casually agree to a stranger's request in a dream? This is just to ask you to record your feelings, in case you give up ten years of life to help you get rid of a stepmother, maybe you won't see us today." ”

Wu Er pushed Song Pan away: "Go! Don't spit out ivory from the dog's mouth." Then he sat down in front of You Longfei, "Then you recall carefully, did you turn back at the fourth intersection after crossing the three intersections of Guqu, Yuanhe, and Langli?"

You Longfei was shocked, and nodded his head like a rattle: "Yes, yes, yes! ”

Zhang Mengde groaned slightly, closed the notebook and spoke: "Can you take us for a walk?"

"When...... Of course...... But can I finish the meal first?" You Longfei looked at the dish he had just prepared, revealing a look of anger that he dared not speak, and at the moment of speaking, half of the bamboo skewer beef was almost eaten by the fat man. This time, without waiting for Wu Er to make a move, Bai Yue had already swung it over with one paw, which frightened Song Pan and quickly withdrew his hand.

It is estimated that You Longfei himself didn't expect to give three men an eye to eat in this life, so he divided five by two, and cleaned the plate with a few chopsticks, which was almost equivalent to swallowing raw, and finally almost choked on it.

The scorching sun was over, and there were fewer people on the campus at noon, Bai Yue seemed to expect that the result was not optimistic, and he looked for a place to wander alone, and the four of them walked outside the school gate, Zhang Mengde patted You Longfei on the shoulder: "It's okay, don't be nervous, we'll accompany you." ”

Wu Er glanced at the time, half past one in the afternoon, from this moment has been walking, it is expected that the time to walk from the school gate to the three intersections of Guqu, Yuanhe, and Langli is 15 minutes, and then without hesitation, the four people did not dare to blink along the sidewalk, and when they arrived at the traffic light at the intersection of Langli Road, You Longfei stopped and pointed to his feet: "From here, it should have been to Yuantuo Road, but now, it can only reach the Jiufangmen Street at the back door of the school." ”

"Okay, let's take a look. Wu Er took a deep breath, in fact, everyone's hearts are not easy, the streets that look ordinary and unremarkable, cars and people, if this kind of thing like a space transfer really happens, it must not be characterized by normal thinking.

The four people deliberately slowed down, walked very carefully, and paid special attention to the changes in the scenery around them, but everything was undisturbed, and even made people wonder if it was because it was too normal but uneasy, there were a total of four forks at the Langli intersection, two diagonally inserted main roads, two auxiliary roads, and the roads were planted with thick French plane trees, which is also a unique feature of the entire Yunjin City, from the intersection of Langli Road to the intersection of Yuantuo Road, at most it is only ten minutes by foot, there is a hairpin bend staircase in the middle, and the four people did not speak, because they really did not find anything abnormal。

"After the small kiosk in front, it should be the Yuantuo intersection, it seems that as long as you don't walk alone, you can still walk out of the school. Song Pan looked at the antique building of the octagonal pavilion in front of him and spoke to You Longfei, the familiar garden rockery and green belt, and his mood was much happier all of a sudden, but Wu Er and Zhang Mengde did not rush to conclusions, until they really stood on the street, and when they saw the street in front of them, Song Pan's whole person was completely frozen, like a thunderbolt overhead, and even Wu Er and Zhang Mengde couldn't help but feel cold down their backs.

In the line of sight, bicycles are parked on both sides of the street, and there is a long queue of dim sum stalls pushing various carts at the back door of the school, and a blue sign stands there quietly, with the words "Jiufangmen Street!"

"Wu Er?"

"Huh?"

"You know what, this feeling of going from the tips of your hair to your toes is scarier than seeing a ghost!"

“......”

You Longfei didn't have much shock, for him, it was really unexpected to go out, back to the school, Wu Er still didn't give up, there must be imperceptible details that were ignored, the four of them chose to go through the back door of the school again, but the result was still to turn back, standing on the long and narrow street, Wu Er had a great sense of defeat for the first time.

“...... I would like to go again. But the paranoia in my heart still prevailed.

When Song Pan heard this, he sat down on the ground: "It's so hot, it will take more than half an hour to walk around, and now there is no place in the body to dry, if you want to go, I can't walk." ”

Wu Er didn't force him, but looked unusually calm, turned his head to Zhang Mengde and said: "Team Zhang, this time we stopped at the Langli intersection, and then tied one end of the rope to You Longfei's body, people may not notice when they are moving, but the rope can show the person's walking trajectory, and then we will naturally know where the problem is." ”

"Whenever possible, it's worth a try. Zhang Mengde agrees with his idea, today's young people are too easy to be killed and give up easily, and it is indeed commendable that Wu Er can have such paranoia to seek the truth.

According to the agreement, Wu Er and Zhang Mengde stopped at the intersection of Langli Road this time, and tied the long rope they just bought to You Longfei's wrist, Song Pan did not follow, he was responsible for waiting for You Longfei at the back door. Everything was ready, You Longfei walked to the next intersection as usual, just as You Longfei's figure turned into the hairpin bend staircase, Wu Er felt the rope in his hand tremble for a while, and his intuition told him that it should be close to the answer!

Song Pan waited at the back door until You Longfei appeared, saw that the rope on his wrist was intact, and hurriedly pulled him back the same way, according to the plan, as soon as He Longfei arrived, he and Wu Er walked from both ends of the rope to the middle, ten minutes later, they met at the rockery in the green belt, but unexpectedly, the rope was in the center of the hairpin bend staircase directly on the east side of the fake mountain to the back door, in other words, You Longfei did not walk through the second half of the stairs at all, but, how is this possible! When the four of them walked together, they definitely remembered to walk the whole staircase before they saw the main road from the west side of the rockery.

"Damn! This is really evil! Could this mountain move?" Song Pan cursed, but his tone suddenly reminded Wu Er of when they came back from eating in the tavern when they were in Sucheng, and they also inexplicably found that the alley that originally entered Fengmo Street was gone, and in the middle of a deep groan, Wu Er muttered out a few words: "Penrose ......"

"What is it?" Song Pan didn't hear clearly, Wu Er looked at the tall rockeries and spiraling down the stairs, and said, "I remember that there was a famous paradox in geometry, called the Penrose Ladder, also known as the Hanging Soul Ladder. It refers to a ladder that is always up or down but does not reach the end, on which the highest point or the lowest point can never be found, in which the human vision is confused by the angle that is always arranged and does not consciously step into a dead loop. ”

Song Pan patted his head, as if he had heard of this kind of thing, but quickly frowned: "I have heard of the Soul Hanging Ladder, but isn't this kind of ladder not able to exist in the three-dimensional space? There seem to be two other similar things, what's they called......"

"The Mobius Ring and the Klein Bottle. Wu Er added.

"yes! Looks like that's the name, damn, it's hard to remember foreign names. ”

"I once read in a special report a sentence that Penrose said when he proposed this ladder, because it was so unbelievable, I was particularly impressed by this sentence, saying, maybe you are passing through a dimension, not only sight, hearing, but also a dimension of thinking, which is between light and shadow, and it comes and goes suddenly, and it is fleeting. ”