Chen Hao zipped his backpack all the way up and fastened it with a click. He glanced down at his old boots; the toes were peeling up, making a rustling sound as he walked.

He didn't say anything, but simply stepped over the threshold.

The wind outside was a little less intense than last night, but it still carried a dusty smell on my face. Susan followed behind him, tightening her shoulder straps and tucking the clipboard under her arm. Carl was the last to come out, carrying a rope roll and muttering, "The sooner we leave, the sooner we'll be back."

Nana stood on the outermost edge, the camera panning across the horizon, data streaming onto the internal interface. She tapped the terminal, and the detector emitted a short beep, indicating a normal signal.

The four people stood in a row, and the base gate slowly closed behind them.

Chen Hao took two steps forward, his foot slipping on a pebble. He steadied himself without turning around. "Have you checked everything? Nothing's missing?"

"Medical kit, pickaxe, water purification tablets," Susan said, flipping through the list in her hand. "They're all here."

“My bag is about to fall apart,” Carl said, shaking his shoulders. “If the strap breaks halfway, you’ll have to take turns carrying it.”

“Then you go in the middle,” Chen Hao said. “There are scouts in front and guards behind, so it’s safest for you to be in the middle.”

“I thought it was because I’m heavy,” Carl grinned.

"You don't even look at how much you eat."

The group began to move. The ground gradually changed from hard soil to soft sand, and they sank in a little with each step. The wind blew from the side, whipping up fine dust that clung to their trouser legs.

Nana walked second, holding the detector in front of her. The green line on the screen moved steadily. "No risk of collapse within five meters ahead; the geological structure is stable."

“Sounds like a weather forecast,” Carl said. “Tomorrow will be sunny, perfect for digging stones.”

"If you don't talk, you can save some energy." Susan wrote something down without looking up.

“I’m just trying to lighten the mood,” Karl patted the detector at his waist. “Otherwise, you’d all be walking around with your heads down, like you’re going to a funeral.”

Chen Hao didn't reply, his eyes fixed on the low-lying hills in the distance. The sun had just risen, casting a white glow on the edges of the hills. They had to cross this wind-eroded area and climb two more gentle slopes to reach their target area.

After walking for about twenty minutes, cracks began to appear in the ground. Thin fissures stretched across the ground beneath our feet, as if something had torn them open.

"Be careful." Chen Hao reached out to stop the three people behind him. "Don't step too deep."

Nana stepped forward and scanned the nearest crack with the detector. "It's about 37 centimeters deep, with a dense bedrock at the bottom. No signs of activity were found."

"So that means it won't suddenly collapse?" Karl squatted down and took a look.

"Not at the moment."

"Then I'm relieved." He stood up and patted his knees. "I was worried I'd fall and get stuck, and you guys would have to dig me out with a pickaxe."

“If you really fall, we’ll take a picture first.” Chen Haomai went over and said, “Post it in the base group chat with the title ‘Who told him to be so cheeky?’”

The group continued onward. The cracks multiplied, but their width and depth remained unchanged. Occasionally, a few exposed gray stones could be seen, their surfaces smooth, as if washed by water for many years.

Susan stopped and crouched down to touch one of the pieces. "Is this... a natural aggregate rock?"

Nana moved closer to the scanner. "The compositional match is 82%, and the preliminary judgment is that it is a weathered and exposed layer. It is recommended to collect samples for analysis."

"Keep it," Chen Hao said. "I'll pick it up when I come back."

“I want to take one back with me right now.” Carl bent down to try it out. “It’s too heavy, I can’t carry it.”

"You want to take a rock the size of a bed board back to base?" Susan laughed.

“You have to have dreams,” Carl shrugged. “What if you find some ready-made furniture along the way?”

They walked for another half hour, and the terrain gradually descended. Ahead, a depression appeared, with traces of a dried-up riverbed in the middle, and the soil cracked into hexagonal patterns.

“There used to be water flowing here.” Susan pointed to the direction of the cracks. “The direction is from east to west, which means that water would accumulate here during the rainy season.”

Nana pulled up a map for comparison. "Based on topographical analysis, this area should receive snowmelt from the hills in the spring, forming seasonal river channels."

“Now it’s so dry it could run a horse.” Karl kicked a clod of dirt, which crumbled into powder.

“That doesn’t mean we’ll keep doing it.” Chen Hao squinted at the distance. “The clouds are drifting this way, and they’re a bit dark.”

“It’s not going to rain, is it?” Carl looked up. “I’ve only been walking for less than an hour, and I haven’t even gotten warm yet.”

“It’s not that I’m afraid of rain.” Chen Hao pointed to the muddy sections on both sides of the riverbed. “Once that kind of mud absorbs water, a person can sink up to their thighs when they step in.”

"So you mean we should take a detour?"

"No detours." Chen Hao walked forward. "Just walk quickly. While it's still hard."

Nana started the navigation and marked a new path; the blue line on the screen followed the edge of the riverbank. She cautioned, "It's advisable to maintain distance to avoid collectively getting stuck in the soft zone."

"Understood." Susan put the clipboard into the waterproof bag. "I'll walk in the middle."

“I’ll cover the rear,” Karl sighed. “Anyway, the worst thing always happens to the rearguard.”

The group moved along the edge of the riverbed. The ground was fairly firm, but with each step, they could feel the looseness beneath the soil. Suddenly, the wind stopped, and the air became stuffy.

After walking about 500 meters, the Nana detector emitted a long beep.

"An abnormal vibration source has been detected 10 meters underground at the 3 o'clock position ahead. The frequency is unstable and the type cannot be identified at the moment."

"What do you mean?" Karl stopped immediately. "Is something moving down there?"

"It could be micro-earthquakes caused by groundwater flow," Nana said. "It could also be biological activity."

"A living thing?" Karl's voice rose. "How big? Does it eat people?"

“Unknown,” Nana replied calmly. “The signal appears intermittently and cannot be continuously tracked.”

Chen Hao glanced at the riverbed. "Whatever it is, we just won't touch it. Let's speed up and get across as soon as possible."

They quickened their pace. But they hadn't gone far when the ground began to change. The once dry mud became damp, and their footprints left shallow indentations that slowly bounced back after a few seconds.

“This spot is no good.” Susan slowed her pace. “If we step any further, we might not be able to pull ourselves out.”

“Then let’s jump over.” Chen Hao spotted a slightly higher, hardened platform and stepped onto it. The platform sank slightly, but he managed to stay steady.

"One at a time, don't push." ​​He called back, "Nana, let the equipment go first."

Nana handed him the detector. Chen Hao took it, turned around, and placed it opposite him. Susan then jumped over, stumbled upon landing, and was helped to her balance by Chen Hao's arm.

"Thank you," she said, catching her breath.

"Does your wrist still hurt?"

"It's nothing." She withdrew her hand. "I just used too much force just now."

“I’m next.” Carl stood still. “You guys check if that side is sturdy first.”

"Sturdy my foot," Chen Hao said. "If you don't jump, you'll have to wade through the mud. It's your choice."

“I choose the third option—you come back and carry me.”

“Then you wait here,” Chen Hao said, turning to Nana. “Throw his pickaxe over here.”

"No!" Carl quickly hugged the pickaxe tightly. "This is my only weapon for self-defense!"

"Then why don't you jump already?"

Carl gritted his teeth, took two running steps, and leaped out. He drew an arc in the air, and when he landed, his right foot sank directly into the mud up to his calf.

"Oh my god!"

He swayed to one side, almost falling over. Chen Hao and Susan simultaneously reached out and grabbed his shoulders, pulling him upwards with force.

"Pull! If I sink any deeper, I'll turn into a fossil!"

The two women pulled with all their might, and Nana joined in to help. Together, the four of them pulled him out of the mud. Karl slumped to the ground, his pants soaked to his knees and covered in black mud.

“I declare,” he panted, “that the biggest takeaway from this expedition is that I have indeed become overweight.”

"Next time I'll let you carry the lightest bag." Chen Hao brushed the mud off his hands. "Now stand up, don't lie down."

“Let me rest for a while.” Carl looked up at the sky. “At least until I dream of a clean bed before I set off.”

“There’s no such thing as a clean bed in a dream,” Susan said, “because you’re lying in the mud.”

"That's why I don't want to get up at all."

Nana suddenly raised her hand to signal for quiet. Her camera turned downstream, and the detector sounded another short alarm.

"The sound of water flowing."

"Where?" Chen Hao frowned.

“I can’t hear it. It’s a low-frequency vibration detected by the instrument.” Nana stared at the screen. “It’s about 800 meters away and is approaching at a speed of 1.2 meters per second.”

“Water coming from upstream?” Susan stood up. “But it’s not raining.”

"It could be a sudden release of seepage water from the mountain," Nana quickly analyzed. "Or some kind of large biological disturbance could have disrupted the aquifer."

"Whatever it is," Carl jumped to his feet. "The question now is—should we keep going?"

Chen Hao looked at the increasingly wet riverbed. The previously cracked earth had begun to bubble, and tiny water droplets seeped out from the cracks.

"Going forward is dangerous, going back is a waste of time," he said. "What do you all think?"

Susan gripped the recorder tightly. "If the water flow increases, this area will turn into a swamp within ten minutes."

“Then there’s no other choice.” Carl grabbed the pickaxe and slung it over his shoulder. “If you can’t run across the water, you can only climb.”

Chen Hao nodded, "Find a high point. That earthen slope over there, if you can get up there, go for it."

The four changed direction and ran towards a raised hill not far away. Their footsteps slammed into the ground, splashing mud. Behind them, the faint sound of flowing water was gradually growing louder.