The dull thud of the ice block hitting the roof hadn't faded when the ground started shaking again.

This time it wasn't just a piece of ice; the entire frozen ground was undulating, as if something was turning over from the depths of the earth. Chen Hao's eyelids twitched. The words from his dream, "Actually... I'm just cold," were still stuck in his throat when Nana yanked him awake with a piece of cold iron pressed against his neck.

"Stop sticking them on!" he shrank back. "If you keep sticking them on, I'll really turn into an ice pop."

Nana didn't let go; instead, she pressed the metal even tighter: "Wake up in three seconds, or I'll electrocute you."

He sat up with a start, his right fingers still stiff—the newly implanted mechanical finger had just started receiving nerve signals, and touching anything felt like touching something through a plastic bag. He shook his hand and found his palm was a little hot, probably because the system's self-heating had activated.

"What's going on outside?" he asked.

“Plants.” Nana had already put on her outer armor, and her electronic eyes scanned the radar interface. “It’s not an ordinary climbing vine, but a purplish-red vine with thorns and tubercles, and its shape is exactly the same as the frozen fruit you ate last time.”

Chen Hao was stunned: "It can grow legs and chase people?"

“Not only that.” She pulled him outside. “They’re converging on the base wall, not fast, but in the same direction—like a hunt.”

The two had just rushed out of the maintenance room when the main passageway was cut in half by a vine as thick as an arm. The thing was covered in wart-like bumps, trembling as if the bumps on a fruit peel had come to life. Chen Hao took a closer look and almost vomited.

"Isn't this the one I chewed on? How come it even comes with after-sales service?"

Just as Nana's sampling needle pierced the thorny tumor, the vine lashed out, flinging the sampler away. She took a half-step back, and a stream of data filled her field of vision.

“The radiation from platinum-iridium ore has altered its biological structure,” she said. “Now it can sense temperature, light, and even… sound.”

"Hearing?" Chen Hao chuckled. "Shall we play some music? How about 'Good Luck' to send it on its way?"

Before he could finish speaking, his ankle suddenly tightened. A thin vine sprang out from a crack in the wall, wrapped around his calf, and dragged him further in. He fell to the ground, using his hands to push himself forward, but another vine seized the opportunity to wrap around his wrist with a force as strong as a winch.

"Nana! This is more of a temporary fix than a real emergency!"

Nana rushed forward to break the vine, but as soon as the robotic arm exerted force, its shoulder joint snapped with a "crack"—the ore damage from the last pipeline repair hadn't fully healed, and the sudden movement caused it to jam. She forced her way through the resistance and tore the vine off, shards scattering everywhere. A pale purple sap oozed from the cut, smelling like rotten strawberries mixed with rust.

"Let's go." She pulled Chen Hao up. "We can't stay here any longer."

The two retreated to the outer wall, leaning against the metal plate to catch their breath. In the distance, the snow-covered ground began to undulate, with raised lines approaching the base, like countless snakes slithering underground.

“They recognize us.” Nana stared at the radar. “The attack targets have precisely locked onto your and my positions, and there are no unusual movements in other areas.”

"Revenge?" Chen Hao wiped his face. "Because I ate its relative? Or because you tore down its wall?"

“Anything is possible.” She pulled up the database. “Plants are at the bottom of the food chain, but they will fight back when pushed to the limit. Look at the distribution of these roots; it’s not random spread, it’s tactical encirclement.”

Chen Hao looked down at his right hand. His five mechanical knuckles were still undergoing adaptive fine-tuning, and the outermost one still had a crooked little engraving—Nana had secretly engraved it last night, saying it was to commemorate the time he used his body to block the pipe.

He suddenly laughed: "Alright, since they want to settle scores, we can't just take the beating."

He pulled out the last packet of chili powder from his tactical pouch; it was dusty and looked like expired seasoning.

"You still keep this?" Nana frowned.

"This is our family's secret recipe." He shook the bag. "It's a potential stimulant, all-natural and additive-free. The worst side effect is runny nose."

"But they are plants, not people, so stimulating their nerves may not be effective."

“You’ll only know if you try.” He grinned. “Science is all about empirical evidence, right?”

As soon as he finished speaking, the wall on the left shook violently, and a large clump of vines burst from the ground, heading straight for the two men's faces. Chen Hao pulled out a flint and steel and ignited the chili powder that was scattered in the air with a "snap".

A flash of fire, and thick smoke exploded.

The pungent smell instantly filled the air, even triggering an alarm in Nana's filtration system. The vines, upon touching the smoke, recoiled violently as if burned, their thorns trembling as if they were all sneezing.

"Effective?" Chen Hao coughed twice.

“Not only that.” Nana’s ears twitched. “They are… retreating.”

Sure enough, the bulges on all sides began to slowly sink, the vines retreated into the cracks in the ground, leaving only a few pools of bubbling purple liquid. The area around the base returned to calm, as if nothing had happened.

Chen Hao slumped to the ground, his mechanical finger twitching uncontrollably, as if a nerve signal had gone awry.

"Looks like they don't like hot pot broth either," he said, panting. "Next time I'll add Sichuan peppercorns and make their ancestors cry from the spiciness."

Nana crouched down to check the blood flow in his arm. The data was normal, but his skin temperature was low. She didn't say anything, but silently turned her vent towards him, squeezing out some residual heat.

"Why do they keep surrounding us?" Chen Hao looked up at the sky. "They don't eat people or take over our territory."

“It might not be an attack,” Nana analyzed. “It’s a warning. They’re building an encirclement and cutting off entry and exit routes, more like they’re driving out intruders.”

"Oh, environmental guardians?" he laughed. "Then I should thank them for being civilized and not just turning me into compost in the soil."

“But we might not be so lenient next time.” She stood up and scanned the surrounding soil. “The root network already covers a range of 100 meters. Forcibly removing it will cause a collapse. We need to change our approach.”

"for example?"

"Use what they fear to deter them in advance."

Chen Hao's eyes lit up: "Sound? Didn't you say they could hear?"

Nana nodded: "The database contains territorial warning audio from the snow wolf pack. The frequency is unique, belonging to the deterrent signals of apex predators. When they dispersed just now, they reacted most strongly to the high-frequency fluctuations."

"Then let them play! Play wolf howls during the day and 'Tantative' at night. They'll either be scared to death or driven crazy by the noise."

“And this too.” He shook the empty bag. “We also need to record the sound of the chili peppers burning, to make a ‘Revenge Plant Buster Compilation’.”

The two immediately got to work. Nana set up the external speaker system, while Chen Hao used the charred remains of a torch to create a ring of marker stakes on the east wall, serving as a makeshift warning line. He tied half a chili pepper shell to the foremost stake, which rustled in the wind.

"See that?" he said through the snow. "That's a border marker! Anyone who crosses it will at least get a pungent smell, and at worst, turn into a spicy snack!"

Nana set the audio program to a timed loop, and the first long howl of the snow wolf began precisely on time. The deep roar pierced through the wind and snow, causing the accumulated snow to fall in a flurry. The ground in the distance trembled slightly, then returned to calm.

“It’s working,” she said.

“That’s right.” Chen Hao sat down against the wall, his right fingertips lightly tapping his knee, as if testing the sensitivity of a new part. “We’re not to be trifled with either. One of us can howl like a wolf, and the other can scatter chili peppers. If we debuted as a duo, we could be on ‘Natural Wonders’.”

Nana glanced at him: "I suggest renaming it 'Human and Machine Wilderness Survival Guide'."

"Add a subtitle: 'How to win a plant war with kitchen seasonings'."

She didn't smile, but a flicker of emotion flashed in her electronic eyes.

Night deepened, and the wind died down. The two crouched under the eaves, gazing at the snow-covered ground that had once undulated so violently. Everything was as quiet as if no battle had ever taken place.

Chen Hao rubbed his face: "You think they'll come again tomorrow?"

"Probability 87.6%"

He grinned: "Then remember to add some rock music. Pure howling is too depressing. It'll be more energetic with some drumbeats."

Just as Nana was about to reply, the ground suddenly trembled slightly.

It wasn't a large-scale arching motion, but a short, rhythmic tremor, like some kind of response.

She looked down at the radar, where a strange pulse sequence appeared on the signal waveform—three short pulses followed by two long ones, with precise intervals.

Like... a certain kind of knocking.

Chen Hao raised his right hand, and his mechanical fingers slowly clenched.