Chen Hao's finger was still on the walkie-talkie when he finished speaking, and then there was silence on the other end. The signal was cut off cleanly, without even a trace of static.

He put away the walkie-talkie and turned to look at Nana: "Can you still get in touch with her?"

"Unable to establish a communication link." Nana stood in front of the control panel, swiping her fingers across the panel a few times. "The electromagnetic interference intensity in the northwest direction continues to rise, and ordinary radio waves are ineffective."

“Then something really happened.” Chen Hao grabbed the backpack on the table and stuffed in a flashlight, spare batteries, and a roll of tape. “Let’s go to the scene.”

Susan walked past, carrying a medical kit: "Aren't you going to wait until the signal is back?"

“We can’t wait.” Chen Hao slung his bag over his shoulder and stretched his shoulders. “Karl said there was light down there, but it wasn’t the kind of light you’d expect from a natural phenomenon. And his last sentence—'It’s too late'—didn’t sound like we could just sit and wait for rescue.”

Nana unplugged the data interface, and with a gentle retraction of the metal arm, the interface closed automatically: "I suggest carrying a low-frequency signal transmitter, which can maintain short-range communication in environments with strong interference."

"Take them with you." Chen Hao nodded. "And also grab two flares, just in case it's too dark to see anything."

The three men stepped out of the control room into the blinding sunlight. The rain from the previous night had just stopped, leaving the ground muddy and making a squelching sound underfoot. They walked in silence, through the maintenance area, around the power station, and straight towards the jungle belt on the outer edge of the base.

On the way, Chen Hao was panting heavily. He had walked less than two kilometers when the back of his clothes was soaked with sweat. He stopped to drink some water and looked up at the sky.

"This awful weather! It looks sunny, but the air is as stuffy as a sauna," he said.

"Humidity is 89 percent." Nana glanced at the reading on her wrist. "There is a localized heat source within three kilometers ahead, which matches the location Karl last reported."

“Then we haven’t gone the wrong way.” Chen Hao wiped his face. “Hurry up, don’t leave Karl in there alone.”

The woods grew denser, the roots intertwined, and the vines tangled. The original path was blocked by fallen branches, forcing them to detour. Susan walked ahead, deftly cutting away the obstructing branches with her knife.

"You mean there really are people down there?" she asked, turning around.

"I don't know." Chen Hao followed behind, panting as he walked. "But to dig a hole 300 meters deep and leave behind something that glows, it couldn't have been done by savages."

“It could also be an abandoned facility,” Susan said. “Left behind by people from before.”

"Then why does it always light up before a disaster?" Chen Hao stopped in his tracks. "When a volcano is about to erupt, a tsunami is about to come, or a storm is about to hit, it flashes. This isn't a warning; it's a greeting."

No one responded.

After walking for another half hour, the terrain began to slope down, and the soil became looser. There was a hint of rust in the air, mixed with the smell of damp, decaying leaves.

"Watch your step." Nana suddenly reached out to stop the two of them. "The soil moisture content is abnormal; there may be underground cavities."

Before he finished speaking, a small section of the ground collapsed in front of him, and soil slid into a dark hole.

Chen Hao squatted down and took a look: "This is the pit Karl was talking about."

The hole wasn't large, about a meter in diameter, with charred edges, as if it had been burned by high temperatures. Faint blue light shone up from below, flashing on and off with a steady rhythm.

“There’s a passage below.” Nana leaned forward to scan. “It’s about twelve meters deep, spiraling downwards, with the inner walls made of artificially cast material and a high-temperature resistant composite structure.”

"Can we go down?" Chen Hao asked.

“Okay.” Nana took out a rope. “I recommend using the three-point anchoring method to avoid the risk of falling.”

"Don't move," Susan pulled her back. "What if it's a trap?"

“A trap isn’t just a hole dug and people waiting to fall into it.” Chen Hao unpacked his backpack. “Besides, we’re already here, we can’t just take one look and go back.”

He tied one end of the rope to a nearby thick tree and fastened the other end to the safety buckle around his waist. After testing the security, he began to climb down.

The cave walls were slippery, and a layer of fine dust covered them when touched. The deeper we went, the more pronounced the blue light became, making our faces appear bluish. Halfway down, our footing slipped, and we landed on a step.

That's it.

Chen Hao steadied himself and turned on his flashlight. Before him lay a narrow path, the walls on either side smooth, their surfaces etched with strange lines. They weren't words, nor patterns, but rather an arrangement of some kind of symbols.

"What are these?" he asked, leaning closer to look.

"Unknown." Nana immediately started scanning after landing. "No matching record found in the database. Preliminary judgment: a status identifier symbol, possibly used to indicate the system's operational phase."

"Sounds like an instruction manual sticker." Chen Hao walked forward. "But who would build an underground corridor and put up a 'Running' sign?"

The passage wasn't long; after a few dozen meters, a circular hall appeared. In the center was a platform with a spherical device suspended above it, emitting a faint blue light. Beams of light projected upwards, forming a slowly rotating ring on the dome.

“This is the light source.” Nana took a few steps closer. “The energy source is still operating, with extremely low output power, but extremely high stability.”

"How is the power supply?" Susan asked.

“Not sure.” Nana shook her head. “There are no external lines and no fuel residue. It’s probably some kind of long-term energy storage unit.”

Chen Hao walked around the platform and found several pieces of rubble piled up on the ground, as if someone had disturbed them.

“Carl has been here before,” he said. “These stones didn’t fall naturally.”

He looked around: "Where is he? Where did he go?"

As soon as she finished speaking, Nana suddenly raised her hand: "Pressure change detected."

Almost simultaneously, Carl's voice came from the side: "Don't touch anything! I just stepped on something—"

He rushed out from another side passage, his face covered in sweat: "Back off! There's a trap here!"

No one had time to react.

With a soft click, like a lock being opened.

The walls around the hall slowly cracked open, revealing several grooves. From each groove emerged a metal arm with a circular probe at the tip, which began to slowly rotate.

"What is this thing?" Chen Hao stepped back.

“Mechanical device,” Nana quickly analyzed. “The motion mode indicates it is active, but it has not yet entered the attack program.”

"Then why aren't you running?" Susan pulled her towards the entrance.

But when they looked back, the passage they had come from had been blocked by a metal plate.

"The door is closed." Chen Hao patted the wall. "It's hard, I can't push it open."

“All exits are blocked.” Nana pulled up the scan image. “Six channels were detected, all of which are currently closed. The system is reconfiguring its internal structure.”

"So we're trapped?" Chen Hao leaned against the wall, panting. "Good grief, they even give us a prison cell experience card for our visit."

“It’s not a prison cell.” Nana stared at the robotic arms. “It’s more like a defense system. They’re watching us.”

"After observing, will you fight?" Karl asked.

“The probability is relatively high,” Nana said. “When the target enters the preset threat range, the response mechanism will be triggered.”

"So, are we considered a threat now?" Susan asked in a low voice.

“It depends on our next move.” Nana looked at Chen Hao. “I suggest we remain still to avoid stimulating the system.”

"Stand still?" Chen Hao grinned. "My legs are aching from standing here, and you're telling me not to move?"

“You can squat down,” Nana said earnestly.

"I'm not a chicken!"

No one laughed.

The robotic arm continued to rotate, emitting a slight hum. A static-filled smell filled the air, and the tips of hair stood on end slightly.

Chen Hao slowly squatted down and leaned against the wall. He stared at the glowing sphere and suddenly felt that it looked familiar.

“This light…” he said, “is it the same signal as before the last storm?”

“The frequency is consistent,” Nana confirmed. “3.7 Hz, with periodic fluctuations. This device is very likely the signal source.”

“So,” Susan whispered, “the red dot that flashes before every disaster is actually it at work?”

“Possibly.” Chen Hao narrowed his eyes. “Then the question is—is it an early warning system, or… the switch that triggers the disaster?”

No one answered.

Suddenly, one of the robotic arms stopped, turned its probe toward them, and a red light swept across the faces of the four people.

"Identification complete." A cold voice came from above, not Nana's. "Access permissions: Unauthorized. Initiate quarantine protocol."

Immediately afterwards, the ground shook.

The sound of metal sliding came from afar, as if more mechanisms were being activated.

“I said,” Chen Hao slowly stood up, “can we talk this over? We’re not bad people, we were just passing by to take a look…”

The robotic arm did not respond.

Instead, they all stopped rotating and pointed neatly to the center of the hall.

Then, one by one, they slowly rose up and aimed at them.