The light above his head flickered, and Chen Hao immediately reached out and pressed his hand on the control panel. The gate didn't open, the countdown didn't start, but the alarm on the protective suit suddenly sounded for half a second and then stopped on its own.

“Signal fluctuations,” Nana said. “The underground interference is stronger than expected.”

"Can it still be used?" Chen Hao asked.

"Currently stable. However, contact may be lost if we go deeper."

"Then let's hurry up." He glanced back at the three of them. "Don't wait until the connection drops before you regret not running away."

Susan tightened her backpack strap, and Carl patted the tool bag at his waist. The four stood in a line, the beams of their headlamps shining on the crack in the ground ahead. The edges of the crack were jagged, as if it had been ripped open by some enormous object. The air was filled with the smell of rust mixed with damp earth, making one's throat dry with each breath.

“Entrance inspection complete.” Nana took a step forward, and the scanner on her wrist lit up green. “There are remnants of metal structure below, but the load-bearing capacity is acceptable. We suggest moving along the left side and avoiding the loose areas.”

"As long as your words are as accurate as a GPS navigation system, that's fine," Chen Hao muttered, and was the first to step inside.

As he stepped onto the first step, the ground trembled slightly. He froze, and the other three stopped as well.

"Was that...an earthquake?"

“No.” Nana looked down at the scan data. “The channel is adjusting. Some kind of balancing mechanism has been triggered.”

"Does that mean this place is still alive?" Susan's voice trembled slightly.

"It's more like a dead person having cramps." Chen Hao continued walking down. "Since we're already inside, we can't just turn back and call it 'Dad' before we leave, can we?"

The steps descended, narrowing with each step. The overhead space gradually decreased, until eventually one had to bend over to move forward. The walls were no longer stone, but grooved metal plates covered with a layer of grayish-green moss. When a flashlight was shone on them, the moss reflected a faint light, as if it were breathing.

After walking for about ten minutes, three forks appeared ahead.

The three passageways stood side by side, almost identical in appearance. The symbols on the walls were arranged in the same way, the floor material was the same, and even the direction of airflow was the same.

"Which one?" Carl asked.

"Whatever." Chen Hao shrugged. "The left end might be a dead end, the middle might be a trap, and the right end might lead to the cafeteria. We don't have a map."

“I have it.” Nana turned on the projector, and a fragmented floor plan floated in the air. “This is a path model reconstructed based on the layout of the early research base. The central passage is most likely to connect to the main control hub.”

"Why should I?" Karl frowned.

"Because the other two doors are closed."

Upon closer inspection, everyone saw that the entrances to the two passages on the left and right were indeed smooth and seamless, while the dividing line in the middle was almost invisible, as if the door had been sealed shut.

“Furthermore,” Nana crouched down, running her fingertip across the floor of the central aisle, “there are scratches left by transport tracks here, 0.3 millimeters deep, all in the same direction. This indicates that manual equipment used to pass through frequently.”

"That sounds pretty promising," Susan nodded.

"Then let's go down the middle." Chen Hao lifted his foot to go in.

"Wait a minute." Carl suddenly reached out to stop him. "I heard a sound when I stepped on that board in front of me."

Everyone quieted down.

A low, rolling sound came from afar, like a stone rolling down from a height, growing farther and farther away.

“The pressure plate triggered a local alarm.” Nana pulled up the audio analysis. “The system is still reacting, but there is no direct threat.”

"Then let's hurry up and leave before it thinks of killing people." Chen Hao led the way into the central passage.

They left a fluorescent beacon every ten meters. The small plastic ball, attached to the wall, emitted a faint blue light. The markings were made slowly, as they needed to confirm the ground's stability with each step. The vibrations in the air grew increasingly intense, as if some machine was operating in the distance.

Twenty minutes later, a narrow corridor appeared ahead.

The walls on both sides are embedded with rusted sensors, and the ground is paved with square stone slabs of varying shades.

"Don't step on them randomly." Nana stopped. "These are pressure mechanisms. Triggering them will release high-speed spikes."

How did you know?

"There are similar designs in the database. This structure was commonly used in defensive fortifications during the ancient Earth period."

"Then do you know how to get by?"

"Try it out."

She stepped forward, lifted her right foot, and gently placed it on the first stone slab. One second, two seconds, three seconds—no movement.

Then take the second step, slowing down the pace. Each step should be spaced about two seconds apart, always staying to the left.

When she reached the fifth block, the sensor on the right suddenly buzzed, and a metal spike shot out from inside the wall, grazing her arm and embedding itself in the opposite wall.

"So close!" Susan exclaimed.

“Found it.” Nana looked back. “The interval must be more than 1.8 seconds, and it cannot deviate more than 30 centimeters to the left. Otherwise, it will trigger a chain reaction.”

“You almost turned into a skewer of meat,” Carl said.

"I'm a robot, I'm not afraid of being roasted."

"We're scared." Chen Hao swallowed hard. "Who's next?"

"I will guide you, and you will follow. Keep the order and maintain distance."

The team lined up again. Nana was in front, Chen Hao followed closely, then Susan, and Carl brought up the rear.

Just as she reached the third board, the hook on Susan's backpack snagged on the wall sensor.

Buzz—!

A row of spikes suddenly shot out from the left wall at an extremely fast speed.

Nana whirled around instantly, pulling Susan back and simultaneously raising her arm to block the flying metal rod. The spikes struck her armor with a piercing thud, sending sparks flying.

"Thanks..." Susan gasped for breath.

"Please keep your bag safe next time."

"I thought it was hung up."

"Now I know."

The group adjusted their formation, moving forward in a single file along the wall. Their movements were slower, but they checked each step carefully. Five minutes later, everyone passed.

"I've finally survived." Chen Hao leaned against the wall and wiped away his sweat.

“This is just the beginning,” Carl said, looking ahead. “It’s only going to get worse.”

The passage continued to extend, its slope increasing. The temperature slowly rose, and breathing became stifling. The communicator automatically sent a pulse signal every thirty seconds, and the feedback point on the screen remained lit.

After walking for nearly an hour, they arrived at a curved corridor.

The symbols on the wall began to glow with a dark red light, flashing on and off like a heartbeat.

“These symbols… are changing,” Susan whispered.

“It’s not a change,” Nana said, staring at one of the groups. “It’s receiving information. Some kind of remote transmission is activating them.”

"To whom should it be sent?"

"I don't know. But the frequency is consistent with the warning records we saw in the lobby before."

"So... this place is still operational?" Carl's voice tightened.

“Some functions are still running.” Nana continued scanning. “I suggest speeding up the process to avoid getting caught up in unknown response processes.”

Chen Hao took a few steps forward, and the detector beeped.

"The space widens after the corner ahead, which may lead to the next area."

Are there any danger warnings?

"There are no clear markings. But an abnormally high concentration of calcium ions in the air usually occurs near high-pressure caves or artificial airtight chambers."

"I don't understand." Chen Hao put away the equipment. "In short, it's not a good omen."

“Never,” Karl sneered.

Susan checked the team members' vital signs. "Their heart rates have all increased, but are still within the normal range. Remind everyone to stay hydrated and not push themselves too hard."

"It's good enough that we can finish the water." Chen Hao unscrewed a bottle, took a swig, and said, "This godforsaken place doesn't even have a rest area."

They continued on their way.

At the end of the curved corridor was a gentle slope that sloping downwards. The beam of light couldn't reach the end; all that could be seen were the increasingly dense symbols on both sides of the rock wall, and the frequency of the red light flashing was also increasing.

Suddenly, Nana stopped.

"What's wrong?" Chen Hao asked.

"The scan showed a sudden change in airflow five meters ahead. It looked like a ventilation opening, but the wind direction was wrong—it was blowing from the inside out."

Is there air movement inside?

“Not only that,” she pointed to the ground. “Look at your feet.”

Everyone lowered their heads.

A thin crack appeared on the once-flat metal floor, slowly opening up. It was less than a centimeter wide, yet it stretched straight into the depths of darkness.

“This isn’t a crack,” Nana said. “It’s a cut. Some kind of sophisticated equipment has just been activated.”

"What can turn on by itself?" Susan took a half step back.

No one answered.

Chen Hao stared at the gap and suddenly felt a chill on the soles of his feet.

He wanted to speak, but found his throat dry.

Just then, all the lights above went out.

Only the helmet's lights were still working.

The four beams of light froze in place, shining on the ever-expanding gap.

A sound came from below.

It wasn't a vibration, nor was it wind.

It is a regular, low-frequency tapping motion.

One shot, pause for two seconds, then another shot.

It's like some kind of signal.

It also seems like... a response.