My childhood friend is in her mature, sophisticated form again today. - Chapter 91

After dinner, Cheng Ran imported the detector data into the computer, and the screen displayed a complete image of the wall. The wall did indeed extend along a distinct arc, eventually forming a smooth closed trajectory at a certain point. That arc resembled the edge of a circle drawn on the seabed with an extremely wide paintbrush, except that the center of this circle was below the water’s surface. A person standing on a boat could not see any end of it; only by moving underwater along its trajectory could one gradually perceive what it truly was.

“It is indeed a circular structure,” Cheng Ran said, pointing to the image on the screen, “but not a complete circle. There is a gap of about thirty meters near the east side, which looks like it was deliberately left out, or it may have been cut off. The walls on both sides of that gap have wear marks and anchor grooves, which are presumably used to install movable grilles or gates.”

Lin Jiqiu shifted his gaze from the screen to the window. The street was deserted, and the streetlights were evenly spaced, illuminating sections of the asphalt road. “How big is that gap?”

“It is about thirty meters wide and extends from the bottom of the wall to the top—if the top does exist. At least within the depth of our probe, there is no sign of a cap; the gap is open.”

Lin Jiqiu stood up, walked to the table covered with data sheets, and looked down at the highlighted gap. It seemed to be the only part of the entire ring-shaped edge that wasn’t filled in, like a narrow but complete passage. Thirty meters—enough for a boat to pass through, or for a person to swim across.

He looked up: “Next time, I’ll go down into that gap and take a look.”

Cheng Ran leaned back in his chair, not speaking immediately. He looked at Lin Jiqiu for a moment, as if weighing a decision. “I’ll go down with you.”

Where are your gill slits?

“I don’t need gill slits. I bring a spare underwater breathing system, and if the sensors detect that the water flow inside the structure is stable, I can descend from the surface in stages.”

Lin Jiqiu looked at him, but Cheng Ran’s gaze remained fixed on him. “If the current becomes abnormal, I will retreat first. This is not a spur-of-the-moment decision; I am more experienced in the water than you think.”

He didn’t try to persuade them further. The lights of the night spread along the curve of the coastline, like a stretched ribbon of light, outlining the boundary between the beach and the nearshore waters as a discontinuous line of light. The mooring ropes on the dock, loosened by the waves, snapped back up, continuously rubbing against the edges of the mooring bollards in the darkness. Lin Jiqiu stood by the ship’s railing, watching the arc of light strung together by streetlights and house lights, like a continuously extending boundary separating the land from the sea.

On the third day, they set off again. As the ship left the harbor, the wind on the sea was weaker than the previous two days. The sky was blue, with few clouds, as if the sea was calming its undulations, making room for a deeper dive. The seawater was cut by the bow of the ship, producing a continuous and even sound. That thirty-meter gap, which had remained still in the images transmitted back by the probe for a long time, was now gradually solidifying from lines on the data into a tangible entity as the distance shortened.

The boat came to a stop at the designated location, and they descended to the water via the rope ladder. As they entered the water, the waves around them broke into fine white foam, then slid past them, like a gentle patter on their shoulders from a wave pushed aside by the sea. Lin Jiqiu led the way, followed closely by Cheng Ran, each carrying their own equipment. They swam along the walls for a while, and the outlines of those walls began to emerge in the dark water, like a dotted line stretched to an endless horizon.

The gap appeared precisely at the predetermined coordinates, where the wall abruptly broke off, forming a straight-edged opening. The interior of the gap was a darker color than the wall itself, as if a layer of denser water had filled it, or as if it were an unobstructed passage waiting for someone to pass through. Lin Jiqiu stopped at the edge of the gap, Cheng Ran standing slightly behind him, his gaze level with Lin Jiqiu’s over his shoulder.

Inside the gap was a wide underwater passage, its walls tapering inwards, the bottom covered with a fine, smooth layer of sediment, like a surface formed by repeated water erosion. The passage narrowed at a depth of about one hundred meters, forming a dome-shaped outline, seemingly sealed off, or perhaps naturally formed. Lin Jiqiu turned on his flashlight; the beam pierced the seawater ahead, illuminating the depths of the passage—where a distinct bright area appeared, like an opening or the entrance to a cavity on the other side.

He glanced back at Cheng Ran, who nodded. Then, the two swam forward together, entering the gap. The flashlight beams traced long, thin arcs on the walls on either side. The walls had parallel stripes, evenly spaced and aligned in direction, as if repeatedly cut by some tool, leaving a series of fine grooves. Cheng Ran swam to the edge of the wall, ran his gloved hand along one of the grooves, then withdrew it and continued forward. There were no unusual sounds, nor any signs of any foreign object triggering an alarm.

The passageway was about a hundred meters long, ending in a more open cavity. Here, the beams of flashlights seemed to lose their boundaries, as if absorbed by an unseen dome. The light spread outwards, illuminating a flat surface and the regular structures distributed upon it—like the bases of pillars submerged underwater, or neatly cut platforms. The water was slightly warmer than outside; the subtle difference felt like a warm current slowly seeping into the space from some deeper source.

Lin Jiqiu hovered in the center of the cavity, the beam of his flashlight sweeping across the wall, pausing at a certain point. It was a recessed area, its edges without obvious damage or deformation, covered with a thin layer of sediment, smooth and symmetrical, like a door. He floated over, Cheng Ran following behind. Lin Jiqiu stopped about a meter away from the “door,” reaching out to touch the edge of the door panel. The sediment peeled off, revealing the metal surface of the door itself—dark gray, rust-free, and smooth to the touch, as if it had just been maintained. The door seal was intact, showing no signs of aging or cracking, the rubber strip still retaining a slight elasticity. There was no keyhole at the door handle, only a recessed sensor area, consistent with the access control system he had seen before. His hand paused at the edge of that sensor area, without touching it, then withdrew, turning to Cheng Ran’s position to confirm that Cheng Ran had also observed the details of the door. The two remained in place for a moment, taking no further action, merely confirming the existence of this location.

They began to rise, traversing the passageways and gaps along the way they had come, until they surfaced. The rope ladder was still there, waiting for them. After climbing onto the deck, Lin Jiqiu removed his mask, sat on the deck, and watched the sky gradually darken.

“That door is still there. Not abandoned, but preserved. The weatherstripping is intact, without wear or sediment. Someone is using it, or at least someone is maintaining it.” Cheng Ran walked up behind him. “If we could open it…”

“Then you can go in.”

Lin Jiqiu looked at him, making sure they were back above the water, then looked away at the distant coastline. Night was slowly covering the sea, like a uniform dark substance spreading from the east, swallowing the remnants of daylight. The underwater trenches, channels, pillar bases, and everything deep within the door cracks remained unaffected; as long as there was no light, they wouldn’t disappear from view. The lights along the coastline were lighting up one by one, like a string of markers lit in a distant place, arranged sequentially along the edge of the continent, each maintaining the same distance and brightness, together forming the long line separating land and sea. He looked at those lights, superimposing them in his mind with the location of the door he had just seen, then stood up and went into the cabin.