The sound of water droplets hitting the metal floor had changed; it was no longer a crisp "tap," but a muffled sound like water hitting mud. Chen Hao stared at the dark liquid in front of his shoe, his nose twitching. The sweet smell from before was still there, but something else had mixed in—like someone had soaked a rusty nail in a vat of vinegar.

He crouched down, dipped his finger in the water on the ground, and rubbed it between his fingers. It was sticky and a little slippery.

“This water is weird,” he said. “It’s even weirder than that pile of chemical smoothies from yesterday.”

Nana had reached the water supply pipe interface, her mechanical fingers touching the valve casing. Her optical eyes scanned the area, and the blue light flickered slightly.

“The lead content in the main water source exceeded the standard by seven times, and the cadmium content exceeded the standard by 6.8 times.” She withdrew her hand. “The pollution source has spread along the underground runoff, and the current coverage rate has reached 60 percent.”

Chen Hao said "Oh" and didn't move.

“You didn’t show the urgency you should have,” she said.

"What's the rush?" He wiped his face. "It didn't explode, right? At most, the sweat from my pee will contain some heavy metals, and I'll just have heavier bones in the future, so I can be used as a weight."

"Long-term intake can lead to neurodegenerative diseases, kidney failure, and damage to the reproductive system."

"That sounds like the last paragraph of a medical report." He slowly stood up. "So? Should we switch careers and open a water purifier specialty store, or should we name our future child 'Anti-Lead No. 1' first?"

"I suggest starting the electromagnetic purification program immediately." She walked towards the control box. "The system can automatically adsorb free metal ions."

“Okay, then you drive.” He leaned against the wall. “I’ll be in charge of clapping and cheering.”

Nana plugged in the main power, and the panel lit up with a green light. Three seconds later, the red light flashed, followed by a "bang" and a burst of sparks. A crack appeared on the side of the control box, and black smoke billowed out from the connector, instantly overpowering the previous sweet and sour smell with a burnt odor.

Chen Hao jumped up in a jolt: "I told you it would explode! I knew it would explode!"

“It didn’t quite meet expectations.” She quickly shut off the main power, “but the outcome is still manageable.”

"You're still being stubborn!" He grabbed the fire extinguisher from the corner and rushed over, pulling out the pin while cursing, "Last time it was the hot and cold pipes connected backwards, this time it's the air purifier exploding. Shouldn't we hold a memorial service for this equipment? Three minutes of silence, and then cremate it."

The dry powder was sprayed into the computer case, and white mist swirled out, mixed with black smoke. Chen Hao coughed, choked by the fumes, and continued spraying while squinting until there was no more movement inside.

"The fire's out." He gasped as he tossed down the fire extinguisher. "The machine's gone, the water's wasted. Should we now declare ourselves officially in the Stone Age? Drinking water by licking rocks, quenching thirst through sheer fantasy?"

Nana crouched beside the wreckage, lifting the casing to examine the circuit board. "The previous modification caused uneven impedance in the grounding line, leading to arcing and breakdown under high load." She looked up. "You connected the wires."

"Hey, you can't just throw the pot around like that!" he glared. "I was just doing it in an emergency! Who knew it would be so temperamental, exploding like that?"

“The system was designed to withstand temporary modifications.” She pointed to a charred chip. “The problem is that you used civilian-grade insulating tape to secure the high-voltage nodes.”

"Doesn't that thing say 'high temperature resistant'?"

"The nominal temperature resistance is 120 degrees Celsius. The actual operating temperature is 210 degrees Celsius."

"...It's a false claim."

"The conclusion is valid."

Chen Hao plopped down on the ground, staring at the pile of charred parts. "We're doomed. We even have to rely on the weather to get a drink of water. This wretched place is terrible. Farming means being chased by plants, storing food means it's going moldy, machines are crashing, and now even the water is poisoned—have we been dragged into some kind of 'unlucky experience package' by some deity?"

Nana didn't respond. A soft humming sound emanated from inside her robotic arm, and the projection interface slowly unfolded, floating in mid-air.

“Activate the offline knowledge base,” she said. “Search keywords: exoplanet water remediation cases.”

The hologram flashed, and more than a dozen data streams appeared. She quickly filtered through them, finally settling on a three-dimensional structural model—a layered cylinder with a honeycomb-like filter layer on the outside, a spiral magnetic tube wrapped around the middle, and a connection to the bioreactor at the bottom.

“A three-stage purification system.” She pointed to the model. “The first layer is physical sedimentation, which removes large particulate matter; the second layer is electromagnetic adsorption, which captures metal ions in a targeted manner; and the third layer is biofilm filtration, which uses engineered bacteria to decompose organic toxins.”

Chen Hao tilted his head and stared at it for a long time, then scratched his ear: "This thing looks like a giant thermos with an indigestible stomach. Can you even build it?"

“Some of the materials are recyclable.” She pointed to the exploded purifier. “The outer metal can be recast into a settling tank frame, and the remaining circuit modules can be repaired and used to power the electromagnetic array.”

"So, we're going to assemble a high-tech toilet from a pile of scrap metal?"

"The metaphor is inaccurate, but the logic is similar."

"Fine," he sighed. "Anyway, I don't have anything else to do. I can't wait until I drink too much and start losing my hair to realize I've prematurely entered old age."

He stood up and began rummaging through the scattered parts. Burnt wires, deformed brackets, shattered sensors... As he picked them up, he muttered to himself, "I shouldn't have been so greedy to buy this cheap, no-name air purifier. I should have just grown a few potted plants; at least they could be used as fertilizer when they die."

"The pothos's absorption efficiency for lead is 0.3 milligrams per kilogram of plant," Nana said. "Based on your daily water intake of two liters, you would need to plant 2,400 pots and harvest them once a month."

"...Don't be so meticulous," he said with a wry smile. "You've extinguished even the last vestige of my romantic fantasies."

The two worked for nearly an hour. Chen Hao sorted and stacked the usable parts, while Nana continuously adjusted the design parameters in mid-air. Suddenly, she stopped.

"The upstream pollution source has been located," she said. "The coordinates are in the northwest karst cave area, at a depth of about seventeen meters. An abnormal metal ion enrichment zone was detected, and the composition is consistent with the old spacecraft debris."

"That damn spaceship is causing trouble again?" Chen Hao frowned. "It's rotten to the core, why isn't it keeping quiet?"

"Long-term groundwater erosion caused the alloy structure to disintegrate, and heavy metals entered the main waterway with the seepage."

"So it poisons people as they die? That's pretty ruthless."

"It is recommended to deploy monitoring probes to seal off the area to prevent further leakage."

"Go ahead and do it, let it do something good before it dies." He waved his hand. "But speaking of which, your brain is really something else. You can pull out a complete plan just by flipping through a database. If I were half as reliable as you, I wouldn't still be struggling to pass my driver's license test."

"You have not registered for the driving qualification test."

"Look, here we go again." He rolled his eyes. "Can't robots learn to play dumb?"

Nana ignored him and remotely activated the cave probe. The monitoring screen switched to a section of collapsed rock wall, showing dark red water slowly seeping out from a crack, its color almost black.

“The pollution continues,” she said. “The rebuilding of the purification system must be accelerated.”

“Let’s get to work then.” Chen Hao flexed his wrists. “Although I’m covered in grease, smell of burning, standing on toxic water, and with a shed that could collapse at any moment… well, compared to the moment I was lying on the chemical smoothie yesterday, I actually feel like getting to work now.”

"The shift in motivation is obvious."

"Don't analyze me." He grinned. "Be careful, or I'll put a virus in your system so you'll say 'You're so beautiful' every time you see a screwdriver."

He bent down, picked up a metal plate, wiped off the dust, and started drawing on the ground with chalk. The crooked lines were barely recognizable as a diagram of pipe connections.

"According to you, the settling tank is here, the electromagnetic zone goes around, and finally leads to that... biological stomach?" He looked up. "What does that thing eat? I'm not going to have to pour yogurt into it every day, am I?"

“The engineered bacteria use organic carbon sources as a nutrient substrate,” she said. “These can be supplied by rotten crops or fermented kitchen waste.”

"Oh, so that's direct connection to the swill bin." He nodded. "Environmentally friendly, and quite down-to-earth."

Nana switched the projection to a construction flowchart, marking the sequence of each step. Her robotic arm fine-tuned the angle to ensure all details were clearly visible.

"The first phase of construction will begin at 6:00 AM tomorrow," she said. "Please put on your protective gear in advance."

Chen Hao finished drawing the last stroke on the ground and blew away the chalk dust. He looked at the simple sketch, then looked up at the complex holographic model in the air.

"To be honest, I still don't understand these high-tech gadgets," he said. "But I do understand one thing—if we don't get them up and running, the next explosion might not just be about machines."

He stood up, dusted off his pants, and reached out to nudge the edge of the projection, turning the bioreactor around.

“Let’s just do it,” he said. “There’s no turning back anyway.”

Nana put away the projector and began to check the tool list.

Chen Hao walked back to the pile of wreckage, pulled out a intact tube from the charred wires, and held it in his hand.

His fingers brushed against the remaining carbonized marks on the surface, then suddenly stopped.

The inner wall of the catheter has a ring of extremely fine silver lines, like some kind of inscription, which shimmer faintly under the light.