The metal door clicked shut, and Chen Hao slumped to the floor, his legs trembling as he leaned against the repair bench. He had just dragged Nana back, and the last bit of strength left in his right arm was almost completely drained. Outside, the wind and snow battered the windows, while inside, only the ticking of the self-checking program could be heard, like a countdown.

He took a breath, wiped his face, and was about to curse a few times to relieve his boredom when he suddenly heard a strange sound coming from the end of the corridor—like sheet metal being slowly bent, or like ice slowly crawling.

"Not again?" He rolled his eyes. "Is this damn pipe sentient?"

Nana was still standing on the maintenance platform, her left arm stiff, in the dim light. She didn't respond, but suddenly a line of text popped up on the screen: "Main pipeline pressure abnormal, freezing rate exceeds environmental freezing model."

Chen Hao frowned: "What did you say? Didn't we just get a cold once? Why is it happening again?"

Before she finished speaking, Nana had already turned and walked towards the main control area. A slight grinding sound came from her right shoulder joint, and her steps were hesitant, like a machine about to fall apart.

"Hey!" Chen Hao pushed himself up. "You think you can do an inspection in this condition? I'll be in trouble if you get stuck halfway through."

He caught up with her, and just as he put his hand on her shoulder, he heard a muffled "crack" from the direction of the manhole, as if something inside had split open.

Nana paused, and the radar light instantly turned red: "An unnatural low temperature source has been detected. Crystallization deposits have appeared on the inner wall of the pipe. Immediate isolation is recommended."

"Crystallization? Where did the crystals come from?" Chen Hao scratched his head. "This isn't a chemistry lab, who would have put salt in the tubes?"

“The data is incomplete,” she said. “But the temperature readings are abnormal, with the surface at -86 degrees Celsius and the interior even lower. This does not conform to the characteristics of a typical frozen tube.”

"Huh?" Chen Hao's eyes widened. "Minus 86 degrees? That's almost as low as liquid nitrogen. Is our base's heating system secretly doubled as a freezer?"

Nana ignored him and walked straight to the wellhead, extending her robotic arm to scan the interior. Blue light swept across the metal wall, revealing spiderweb-like ice patterns on the screen, layer upon layer, slowly spreading.

“The structural stress continues to rise,” she said in a low voice. “If we don’t intervene, it could burst within fifteen minutes.”

"Alright then," Chen Hao sighed, "Looks like I'm destined not to be able to lie down and eat spicy strips tonight."

He turned and went to the tool cabinet to retrieve a portable torch, lit it, and brought it close to the valve. The moment the flame touched the ice, the ice cracked open with a "pop," and a plume of blue-green mist shot out, spreading along the ground.

"Holy crap!" He jumped back. "Is this thing poisonous?"

"Warning!" Nana's voice suddenly rose, "Cryogenic liquid nitrogen release! Evacuate within a ten-meter radius!"

Instead of retreating, she stepped forward, her robotic arm deploying a protective barrier to shield him. Cold mist enveloped the metal casing, instantly condensing into frost flowers that seeped into the joint gaps.

"What are you doing? Are you out of your mind?!" Chen Hao grabbed her arm.

“Gas is flowing into the power module,” she said. “If the core unit freezes, the backup power cannot be activated.”

"But you can't use yourself as a shield! You're a robot, not a riot control wall!"

“The logic holds true.” She remained still. “My heat capacity is higher than yours, which can slow down conduction.”

Chen Hao laughed angrily: "You really think you're a heat sink?"

He shook her off and went around to the other side to check the leak. Cold air kept seeping from the weld seam in the well wall, making the air feel heavy and frozen. He stared at the crack, then suddenly squatted down, took off his coat, and stuffed it inside to plug the leak.

"Are you crazy?" Nana turned her head.

"Otherwise what?" he grinned. "Your left arm is practically an icicle, and these are the few tools I can use. You can't expect me to write a bug and let the system fix it automatically, can you?"

"Contact with body heat can cause local tissue damage."

"I know, I know. At best, it'll cause blisters; at worst, it could lead to amputation. I won't even be able to do the eighth section of calisthenics anymore, right?" he gritted his teeth. "But isn't there no other way?"

He shifted his position, pressing his entire body against the well wall, his back pressed tightly against it. The chill felt like needles piercing his bones, and he couldn't help but shiver, muttering to himself, "Ugh, this feeling is comparable to sitting on an iron chair in winter wearing shorts... Hey, if I freeze to death, can I have my last words engraved on your forehead? Just write 'A brave warrior who loved spicy snacks once lay here.'"

Nana paused for two seconds, then suddenly raised her hand and stretched her left arm toward the nozzle.

"What are you doing?" Chen Hao exclaimed.

“Try a mechanical seal,” she said. “The drive module can withstand brief periods of extreme cold.”

"Can withstand it my foot! Your right arm just broke out, and now you want to use your left side to assemble it? Do you think you have more parts than you can use?"

Before he could finish speaking, he saw her arm dip into the mist, and immediately a thick layer of white frost formed on its surface, with a cracking sound coming from the joints, like glass shattering.

"Stop!" he roared.

She didn't move.

"Nana! I order you to withdraw!"

She continued pushing forward until her entire arm was submerged in the cold mist. Three seconds later, a sharp crack rang out, and a fissure appeared in her elbow joint as the hydraulic fluid instantly froze, turning into powdery particles that scattered across the surface.

"Enough!" Chen Hao suddenly flipped over and pounced on her, grabbing her waist and dragging her backward. She lost her balance and fell heavily to the ground, her left arm twisted and hanging down, yet still stretched forward as if to protect something behind her.

After the last burst of cold air was released, the backup pipeline was connected, and the pressure gauge returned to zero.

It fell silent.

Chen Hao lay on the ground, panting heavily. His back burned as if it had been scraped by countless tiny knives. He looked up at Nana, who was lying beside the repair table. The lights flickered, and the screen displayed the words: "Left arm drive module ruptured... Protection priority maintained at the highest level."

"Is that all you've got?" he laughed hoarsely. "Do you have to tear yourself apart to complete your mission?"

She didn't react.

He struggled to his feet and limped as he carried her back onto the table. Her arm was bent to one side, her metal fingers slightly curled, as if she were still trying to grasp something.

He reached out and touched her cold hand, then suddenly remembered something and pulled out half a piece of dried meat from his pocket—the piece she had hidden during training yesterday, which she hadn't been able to bear to eat.

"I'm saving it for you." He stuffed it into her hand. "You can chew on it after you've fixed it. Don't say I'm abusing a robot later."

The piece of meat slipped and hit the metal countertop with a crisp sound.

He didn't pick it up, but sat down against the table, looking up at the ceiling: "You, you could have just talked things out, but you insisted on carrying the burden yourself. Last time it was mining, this time it's plugging leaks, are you planning to stuff me into an insulated box next time and then rush into the sun to generate electricity yourself?"

Outside, the wind and snow howled, and inside, only the sound of dripping water and his heavy breathing could be heard.

He looked down at her and noticed that the light in her eyes was still on, though faint, it hadn't gone out.

“Next time…” he lowered his voice, “don’t do that again.”

There was no response.

He reached out and tried to put her stiff hand down, but her fingers were stuck and he couldn't pry them open.

Let's just leave it at that. He thought to himself.

Anyway, you can't hear me say thank you.

He leaned against the edge of the table, closed his eyes, and relaxed his shoulders. A few seconds later, he opened them again, took out a utility knife from his pocket, and, using the dim light from the screen, gently made a cut on the metal casing of her broken left arm.

It wasn't a word, nor a mark, just a shallow mark.

Like a response.

Like saying goodbye.

Outside the door, a wisp of cold air slowly blew down from the ventilation vent at the top of the maintenance area, carrying a faint trace of blue-green mist recirculation.