...... is this," the other three asked almost simultaneously.

But Frey didn't speak, just glanced at the cell number and began to look down for the key.

With a click, the lock of the cell in front of them was opened.

"How do you have the key here!?" Rare asked, unable to hold back any longer.

However, Frey did not answer him, and instead led the way.

"That's not what you should be concerned about right now, and even if you know the answer, it won't help you find your friends. Frey slowly spat out these two words as he held up the magic lamp and examined it on a wall, "The point is that we're in." ”

"That's right. Cynthia also said, "The most important thing right now is to find that vent." As she spoke, she raised her wand in her hand, scrutinizing the wall as she slowly groped with her hand, even though it was cold.

Alan and Riel had no choice but to start inspecting the remaining wall as well.

The structure of the cell was very simple, and the remaining three walls were not large except for the fence gate, so they could be inspected quickly. Strangely, none of them found anything resembling a secret door or vent.

"That's weird......" Alan frowned, "it doesn't make sense......"

Frey and Cynthia also re-examined, but found nothing. And this time they checked inch by inch, from top to bottom, from left to right, not sparing a single corner.

"Could it be that this clue was made up by Doug on the spur of the moment?" asked Riel.

"No way. Alan shook his head, "It's really much colder here than other places, and you see......" said Alan as he pulled a hair from his head, lifted it above his head, and let go of his hand.

Through the not-so-bright light, Riel saw that the hair did not fall out directly, but swayed left and right in the air for a while before hitting the ground.

"It's subtle, but it's windy. Allen said. In fact, he felt that there was indeed a wind blowing gently from the moment he entered, but it didn't seem to be felt by Riel.

"But we've searched every nook and cranny of this room......" Riel shrugged, "it's not unlike that one."

Indeed, Alan looked around again, and found that all the cells were arranged in the same way, and at a glance it was clear that there was only a small stone bed on the right side against the wall.

"If there's one thing that's different, it's that Doug has a quilt on his bed. Riel said again.

"Stone bed?" Alan suddenly remembered Doug's words, "wait...... Could it be the problem with this stone bed!?"

Thinking of this, he didn't care about the cold, and just lay on this cold stone bed.

"What are you doing here?" Riel looked at him puzzled.

Alan didn't pay attention to him, but lay on it and carefully felt the change in the airflow.

Sure enough, he turned to the side and found that there was indeed a stream of air blowing into his ears from the bottom up.

He crawled out of bed, put his hand on the junction of the stone bed and the floor, and found that this wind was from here.

"We're all going to have to pay attention to these walls...... Alan chuckled, "but Doug didn't say there was a secret door in the wall...... Since there is usually wind in the house, we will think that it is blowing in through the window or door, and we preconceived that if there is a secret door, it must be on the wall, but in fact, ......"

At this point, Alan paused, but instead stretched out his hand and began to use the levitation charm.

"Give me a hand. After trying it out, Alan noticed that the stone bed was much heavier than he had imagined, and said.

When Cynthia and Frey heard this, they pulled out their wands and began to cast a levitation spell on the stone bed.

I saw that the stone bed was moved away little by little by the three of them, and the wind suddenly became stronger, and a black rumbling hole began to slowly appear. Seeing this, the three of them instantly became energetic and completely moved the stone bed to the side.

"Whew......," Alan continued, breathing a sigh of relief, "but in fact, it could also be on the ground. ”

"Wow!" Riel had seen the inside of the hole by the light of the fire.

The hole that appeared in front of them was almost half the width of the stone bed, square, just enough for two people to get into. Looking inside, a neat row of steps stretched diagonally downward, with no end in sight, as if extending to the ground.

"It's here!" Riel cried again, "how did you think you'd be down here?"

"It's very simple......," Alan smiled again, "since there is no one on the wall, the eight achievements are on the ground...... It's a simple method of elimination. ”

"Oh......" Alan said this, and Riel suddenly felt that it seemed to be such a simple truth.

"Actually, it was Doug's words that really drew my attention to the ground......," Alan continued, "do you remember what he said...... That's right, it was when he lay down that he felt the wind blowing in his ears...... As you can see, I went to that bed to confirm that. ”

Only then did Riel understand what Eren was doing with his strange behavior.

Several people looked around the entrance of the cave for a few more moments, all hesitating. Because they don't know where this secret path leads, whether it's a trap, or if it can really lead them to the truth.

In the end, it was Frey who spoke first: "Let's go." With that, he took the lead and walked in.

Cynthia followed, followed by Alan and Riel.

The slope of this step is steep, so Frey doesn't walk very fast.

At first, Alan wondered if it had been dug up by the people who had been locked up here in the past to escape, but now it seemed impossible, because as he walked, he observed the surroundings and found that this dark passage was actually very neatly built, and it was reinforced with blue bricks on all sides, except that it led straight to the ground and there were no magic lamps on either side, and it was somewhat similar to the passage into the Elemental Tower.

"Who dug this tunnel, and the people who were locked up here before?" Riel asked the same question.

"Not true. Alan shook his head, "If it was dug by the people who were locked up here, it would be impossible to dig the steps so neatly, right?"

"Hmm...... It seems like this......"

"And look in the direction of this dark passage,......" Alan pointed at their feet again, "if you were locked up here, where would you dig to get out?"

"Uh......" Riel realized, "Go up!"

"That's right...... But now ......," Alan thought.

"Who built this tunnel...... Rare asked, stunned.

After walking along the staircase for nearly a quarter of an hour, they suddenly felt the slope of the staircase slowly slow down, and finally at the end of the staircase, a straight forward aisle appeared in front of them. The aisle began to widen a little wider, allowing the four of them to walk side by side, and there were magic lamps on either side of the wall every short distance.

"What's going on......" Riel began to mumble again.

They walked like this for about a quarter of an hour, expecting to see an exit, but there was another staircase similar to the one before, only this time straight up.

Even Alan is a little confused now.

They had no choice but to climb the stairs slowly and upwards again.

This time, however, they didn't walk long up, and it was only about ten minutes before Frey, who was walking in the front, suddenly stopped.

"What's wrong?" asked Allen.

"It's over. Frey's voice came.

"It's the end?" Riel was stunned for a moment, and said in his heart, "Isn't it a dead end after walking for a long time?"

But Frey fumbled around the wall diagonally above him, and after pushing hard, a blinding light shone in, and it grew brighter and brighter.

A few people breathed a sigh of relief, and it seemed that they had finally arrived at the exit.

The four men walked out in turn, and only then did they find that they seemed to be halfway up a hill, and in front of them was a huge crescent-shaped lake, and on the other side of the lake was another mountain about the same height.

"Where is this?" asked Riel, looking around.

However, Frey did not answer him, and looked at the lake in front of him a little stunned, and after a long time said, "This is the ...... Back Mountain?"

"Back Mountain?"

"Yes...... It's the other side of the cliff that you can see...... "Frey explained, "remember the cliff that looked like it had been cut by a knife, and that was the other side of the mountain......"

"What?" Alan was stunned for a moment, thinking carefully about the road he had just walked, as if he understood something, "In other words, we just passed through the underground of that valley?"

"Yes...... It's a little hard to believe, but there's nothing wrong with this shape......" Frey stared at the lake in front of him, "It's the crescent lake that clings to the east side of the back mountain. ”

Alan didn't ask any more questions when he heard this, and took a closer look at the lake.

The lake was literally like its name, crooked, lying like a giant crescent moon between two mountains, with its back to the back mountain, holding the other hill in its arms.

It's just that now the whole lake is frozen.

"But what's going on...... Fry's brow furrowed as he stared at the lake, "I was here once last winter, and the lake never freezes......

But when they looked at their feet, they couldn't help but feel nervous, because the ground here was also covered with thick ice. Luckily, the ice didn't freeze them, unlike the ones in the castle.

The mountain on the other side of the Crescent Lake looks even more eerie, covered in snow and ice from the top to the bottom of the mountain, and you can see that it is still snowing there.

"It seems...... All the answers are on that mountain. ”