The red dots are still spreading.

Chen Hao stared at the metal plate; the red edge of the blue light resembled a drop of oil floating on water, slowly spreading. He had just lifted his foot to step down when Nana reached out to stop him.

"Wait a moment."

"What's wrong now?" He pulled his foot back. "Didn't you just say that I could come in once the door was open?"

“The door is open, but that doesn’t mean it’s safe.” Nana looked down at the screen on her wrist. “There’s a radiation signal below, not strong, but it’s rising. The temperature is also getting higher.”

Susan walked to the edge of the cave and peeked inside. "Is the wind blowing up from below?"

“It’s thermal convection,” Nana said. “It’s cold up there and hot down there, and the air is circulating. When we go down, we’re going against the thermal flow.”

Carl leaned against the wall, panting. His left arm had just been bandaged, and his clothes were still damp with the medicine. "So, it gets hotter the further down you go?"

"Currently, it is predicted that the ambient temperature will rise by three to five degrees Celsius for every ten meters of descent." Nana closed several unnecessary system interfaces. "The protective suit can hold out for a while, but not for too long."

Chen Hao touched his forehead; he was already sweating a little. "So we're walking into a furnace now?"

"To be precise, we've entered an unrecorded active zone." Nana activated the detection mode. "I'll go first, you guys follow closely."

She finished speaking and stepped onto the stairs. The metal steps hummed slightly, like iron sheets being heated underfoot. Chen Hao followed closely behind, with Susan and Carl bringing up the rear. The four of them formed a line and slowly descended.

The stairs were narrow, allowing only one person to pass at a time. The walls were made of dark gray alloy, with some areas turning reddish, like the bottom of a burnt pot. Chen Hao reached out and touched it, then immediately withdrew his hand.

"It's so hot."

"Don't touch it," Nana said from the front. "This material conducts heat quickly, and the surface temperature has already exceeded sixty degrees."

"You're still walking so steadily?" Chen Hao asked, panting. "You're made of iron, I'm not."

“I’m a machine.” Nana glanced back at him. “You’re fat, with a thick layer of fat, so you should be more heat-resistant.”

"That's for insulation, not for heat dissipation!" Chen Hao tugged at his collar. "I feel like a steamed bun in a steamer right now."

“Then you better not crack,” Susan said from behind, “otherwise we’ll have to take a detour to pick up the filling.”

Carl chuckled, then immediately choked, coughing twice. "Can you guys stop talking about food? All I can think about right now is hot pot."

"The hot pot is good." Chen Hao looked up. "If only we had a bowl of chilled plum juice right now..."

"Shut up." Nana suddenly stopped.

The group immediately fell silent.

"What's wrong?" Chen Hao asked in a low voice.

"Ten meters ahead, the air composition has changed." Nana stared at the data. "Oxygen levels are decreasing, while carbon dioxide and sulfides are increasing. We'll have to switch our breathing system if we go any further."

She raised her hand and made a few movements on her wrist. A soft beep came from inside the helmet, and the oxygen supply mode automatically switched. The others followed suit and adjusted their equipment.

"Don't talk anymore, conserve your oxygen." Nana continued walking forward. "Visibility will decrease, just keep an eye on my back."

Chen Hao nodded, then realized that no one could see his action, so he simply shut his mouth.

The lower he went, the stuffier the air became. His helmet visor began to fog up, and his breath condensed into a white film in front of his eyes. He rubbed his face a couple of times and could barely make out Nana's silhouette in front of him.

The red light from the walls grew stronger, as if it were emanating from within. The steps beneath their feet were no longer level; some sections had sunken in, and stepping on them produced a creaking sound.

"How long has this place been without repairs?" Karl asked in a low voice.

“No one has repaired it,” Nana said. “This structure doesn’t conform to any known base construction standards. It’s more like it grew out of nowhere.”

"Grown?" Chen Hao was taken aback. "Metal can grow?"

“A crystallization process catalyzed by some kind of energy,” Nana explained. “It’s like water freezing, only faster and with a more complex form.”

"So we're walking on a piece of metal that's 'growing'?" Karl's voice was a little tense.

"Theoretically, yes."

"Theory my ass!" Chen Hao stumbled and nearly fell to his knees. He grabbed the wall for support, his palm immediately burning with pain. "Who designed this lousy road? There's not even a handrail!"

“No one designed it.” Nana turned around and pulled him back. “It formed on its own.”

"Couldn't you have considered human engineering when it was formed?" Chen Hao said, waving his hand. "At least leave a ramp!"

No one answered. The air grew heavier, each step feeling like pushing against a wave of heat. Chen Hao's breathing echoed inside his helmet, growing louder and louder.

"Did you hear that?" Susan suddenly asked.

"What?"

“A sound.” She slowed her pace. “Like… a heartbeat.”

Nana stopped and brought up the audio monitoring. The waveform on the screen was fluctuating; there was indeed a low-frequency vibration, with irregular intervals, but it was always present.

“It’s not a heartbeat,” she said. “It’s an energy pulse. The frequency is unstable, and the intensity is changing.”

"Is it the same as the node above?" Chen Hao asked.

“They’re different.” Nana compared the data. “The one above shows regular oscillations, this one shows random jumps. And…” she paused, “it’s responding to us.”

"A response?" Karl tensed up. "What do you mean?"

“With every step we take, the pulse frequency shifts slightly.” Nana looked around at the walls. “It’s sensing our presence.”

Chen Hao was silent for a few seconds, then laughed. "So this place is alive? We're crawling inside the belly of a metal monster?"

“The analogy isn’t accurate,” Nana said, “but it does possess some kind of rudimentary sensory ability.”

“What if it thinks we’re parasites?” Carl whispered. “Would it just seal off the passage?”

"Then it depends on who runs faster." Chen Hao patted him on the shoulder. "Anyway, you're lighter than me, so you can bring up the rear."

“Stop fooling around.” Susan stared at the rock wall. “There’s a crack here.”

She pointed to the right wall, where a thin crack was slowly opening, emitting hot air. Nana scanned the area and gestured for them to go around it. The four of them moved close to the left wall, less than half a meter from the crack. The heat wave hit their protective suits, making a hissing sound.

"If this keeps up, the clothes will burn." Chen Hao touched the outside of his arm.

“The protective layer can hold for another forty minutes,” Nana said. “After that, we must find a safe haven.”

"What can you do in forty minutes?" Carl gasped. "We haven't even covered half the distance."

"Then let's hurry up." Nana quickened her pace.

They continued their descent. The thermometer showed the outside temperature had reached 85 degrees Celsius, and the cooling system inside the helmet was operating at full capacity, emitting a low hum. Chen Hao's vision was a little blurry, and sweat trickled down his neck and into his collar.

“I said…” he took a breath, “shouldn’t we take a break?”

“No.” Nana stared ahead. “The energy fluctuations are intensifying. If it suddenly erupts, the entire passage will collapse.”

"Then you make us run faster but won't let us rest? Are you trying to kill us with exhaustion?" Chen Hao's voice trembled. "I'm warning you, if I die, you won't get away with it either. You'll have to carry me out of here!"

“I won’t carry it.” Nana said without turning her head. “I’ll leave you here as a marker.”

"You're so thoughtful." Chen Hao gritted his teeth and continued walking.

Finally, the steps came to an end. A small platform appeared ahead, about ten meters wide, with the surrounding rock walls glowing a dark red. There were several grooves in the ground, filled with a luminous liquid that shimmered, its color shifting between blue and red.

"What is this?" Susan crouched down to look.

“Uncertain,” Nana said, collecting a sample. “But its energy characteristics are consistent with the pulse we just heard. It could be the transmission medium.”

"Will it explode?" Carl asked from a distance.

"It's stable right now," Nana recorded the data, "but I advise against getting close."

Chen Hao plopped down on the ground, leaning against the wall. "Finally, I have somewhere to sit... Ouch, my back!"

"Don't touch the wall," Nana immediately reminded her.

He quickly moved away. "This wall can eat people?"

“The surface temperature exceeds 100 degrees Celsius,” Nana said. “You’ll get burned.”

"I'm almost cooked through." Chen Hao lifted a corner of his helmet and wiped his face. "If we keep walking like this, I won't even need to take off my clothes; I can just peel off the skin and eat the meat."

“Don’t joke like that.” Susan checked the weapon’s condition. “The barrel is starting to deform.”

"Your gun can't even withstand it?" Chen Hao asked in surprise.

“All electronic devices are overloaded.” Nana checked the system status. “My right arm repair program has stopped; power is being prioritized for the detection module.”

"So, you're now a crippled robot?"

“I’m just functionally limited,” Nana corrected. “Unlike some people who are functionally incomplete from the beginning.”

“You’re hurting me,” Chen Hao said, pointing to himself. “I’m the core decision-maker for the team.”

"You almost fell into the crack just now."

"That was an accident!"

"This is the third time."

"...Why do you remember it so clearly?"

Nana ignored him and continued analyzing the data. Suddenly, her screen flickered, and the waveform fluctuated violently.

“There’s a problem,” she said. “The energy frequency has changed. It’s no longer a single pulse, but multiple superimposed ones. And…” She looked up into the depths of the platform, “something is starting up over there.”

Everyone followed her gaze. At the end of the platform was an archway, which had been closed, but was now slowly opening, revealing a dark passage behind it.

"Who opened it?" Carl's voice was strained.

“It wasn’t us,” Nana said. “It was an automatic system response. It’s probably because we triggered some condition.”

"for example?"

“For example, walking in alive.” She stood up. “Ready to move on. A new path has opened up.”

"That's it?" Chen Hao's eyes widened. "We haven't even caught our breath!"

“You can stay if you don’t want to leave.” Nana stepped forward. “We will erect a monument for you and write ‘Here lies a warrior who was afraid of the heat.’”

"Do you have to be so mean?" Chen Hao struggled to his feet. "Let me tell you, if I get heatstroke, you'll be the first one I drag down with me."

“You can’t drag it.” Nana had already reached the archway. “Come in, the new area awaits us.”

Chen Hao cursed and followed. Susan and Carl exchanged a glance and then went inside as well.

Inside the archway was a wider passageway, its walls made entirely of luminous metal that constantly shifted in color. The floor was flat, but subtle vibrations could be seen.

“This place is even more eerie than before,” Karl whispered.

"Don't speak." Nana stared ahead. "The energy field is too strong; it will affect your judgment."

They walked about twenty meters when Nana suddenly stopped.

"What's wrong?" Chen Hao asked.

She didn't answer, her finger swiping rapidly across the screen. A few seconds later, she looked up.

We were wrong.

"What's wrong?"

“This isn’t a new area,” Nana said, her voice lowering. “It’s part of the same system. But the node we adjusted… it’s just a surface reaction. The real core has always been here.”

"So everything just now was a ruse?" Susan gripped her weapon tighter.

“It’s not a cover-up,” Nana said, looking at the data. “It’s misleading. Someone—or something—doesn’t want us to find out about this place.”

Chen Hao swallowed hard. "So... do we mean we've trespassed into someone's backyard?"

Before Nana could answer, the ground suddenly shook.

The walls of the passage ahead began to move, the metal flowing like liquid, rearranging itself. A new door frame slowly took shape, its interior radiating a deep red light.

The door opened.

There was a figure standing inside.

It has a mechanical structure and a human-like shape, but its entire body is covered by a flowing metal shell. Its head has no facial features, only a ring of lights that is slowly rotating.

It raised its hand and pointed at them.

Chen Hao took a step back.

"This thing... is it your relative?"