The sound of the metal door closing still echoed in his ears. Chen Hao didn't turn around and walked away. Susan followed closely behind, Carl lagged behind panting, and Nana walked at the very back of the group, her blue eyes scanning the collapsed entrance behind her to confirm that there were no aftershocks.

They followed the path they had come by towards the sea, but halfway there they found it had collapsed. A small slope of rubble blocked their way. Carl glanced at the waterproof box, then at his injured leg, and muttered, "Do I really have to carry this thing?"

“If you want to swim back, you don’t need the box,” Chen Hao said, already probing the ground with a stick. “You can still walk this way, but it’ll be a bit of a detour.”

Nana activated the infrared scanner and pointed out a safe route. The four of them lined up and took turns carrying the boxes forward. When Susan took over from Carl, the box almost slipped off; she cursed and tightened the shoulder strap.

Upon reaching the shore, the boat rocked violently in the waves. The mooring rope had loosened and was about to snap. Without a word, Chen Hao jumped into the water. His soaking wet trousers clung to his legs, making him shiver from the cold. He rewound the rope around the stake, tying three tight knots.

"You're quite skilled at this," Susan said, handing the box down.

"I learned this by walking the dog on a leash before," Chen Hao grinned. "Back then, my golden retriever always loved to run into the river."

The boat wasn't big, but it could seat four people. As soon as Nana boarded, she went straight to the control panel, swiping her finger across the screen. The main control light flashed green, the engine hummed, and then shut off.

"What's wrong?" Chen Hao leaned closer.

"Power module voltage abnormality." Nana stared at the data stream. "The system indicates that the energy converter is overloaded."

Carl leaned against the bulkhead and reached out to touch the outer shell. "Hot, it's burning."

"Can't it be fixed?" Susan asked.

“There’s a way.” Nana pulled up some information. “The emergency technical files mention similar faults, and temporary components can be used to replace the fuse structure.”

"So, do you remember how to do it?"

“The database has maintenance protocols,” she said, “but welding is required, and the operating environment needs to be stable.”

The waves outside were quite large, causing the boat to rock back and forth. Chen Hao glanced at his toolbox, then at the swaying light overhead. "We have to stay steady, even if we can't. We're still far from the base; we can't just drift here waiting to be fish food."

Susan pulled out the welding torch and insulating tape. Carl unscrewed the equipment casing, his hands trembling slightly. An old injury slowed his movements, but he didn't stop.

"Are you sure you can do it?" Chen Hao stared at him.

"Enough with the nonsense," Carl gritted his teeth. "We've already taken it apart, do you think we can put it back halfway?"

Nana began reading the circuit diagram, reciting the parameters aloud. Chen Hao held down the toolbox to prevent it from sliding. Susan shone her flashlight, the beam swaying with the boat's movements.

The first time it was welded on, the ship suddenly rocked, and the joint broke open.

"Again." Carl wiped the sweat from his brow.

The second time, halfway through welding, his arm twitched, and the weld point became crooked.

"Can you handle it?" Susan asked.

“What do you think?” Karl glared at her. “Change people now? Who knows how to do this?”

Nana crouched down and handed over a copper wire. "The third guide bridge connects here, at a 30-degree angle."

Carl took it, took a deep breath, and began welding for the third time.

Chen Hao braced himself against the workbench, his entire body acting like a human cushion. Susan fixed the light in the corner and held onto the support frame herself. The boat was still rocking, but this time it was more stable.

A spark flew the moment the welding torch touched the metal. Karl held his breath, his hand remaining steady. After finishing, he leaned back, slumping against the bulkhead.

"Did it work?" Chen Hao asked.

"Try it and you'll see." Nana connected to the test program and tapped her finger lightly on the panel.

A few seconds later, the main screen flashed green. The engine emitted a deep hum, like a wild beast waking up, and slowly began to run.

"It moved!" Susan slammed her hand on the table.

Carl grinned, then frowned and clutched his arm. "Damn it, this arm is going to be useless sooner or later."

"It's okay if you're crippled." Chen Hao patted him on the shoulder. "The base will provide you with a robotic arm. Maybe you can even win a weightlifting championship."

“You’re the one who needs a robotic arm,” Karl scoffed. “Getting this fat, your heart will give out sooner or later.”

"This is just happy weight gain," Chen Hao said, rubbing his belly. "You only gain weight when you're stressed. Look at you now, you're as thin as a bamboo pole. You must have something to hide."

Susan rolled her eyes. "Can you two shut up? You're arguing as soon as it's fixed. Be careful it doesn't explode again."

Nana didn't join the banter; she was adjusting her course. "Current speed restored to 60%, expected to exit the fog zone in five hours."

"Five hours?" Chen Hao walked to the bow of the ship and looked at the gray sea ahead. "That's unlikely. This weather doesn't look like a good sign."

The sky was overcast, with low-hanging clouds. The horizon was indistinct in the distance, the sea a greyish-blue hue, waves crashing one after another. The boat cut through the water, making a rhythmic splashing sound.

Susan checked the supply box. "The waterproof box is fine, all the documents are there. It's just that one of the spare batteries is missing; I don't know if it got lost on the way."

"Forget about the batteries," Carl said, leaning against the hatch. "Let's get to shore alive first."

Chen Hao glanced back at the control panel. "Nana, will the system suddenly stop working again?"

"It is currently operating stably," she said. "But it may still be interrupted if it encounters strong electromagnetic interference or a violent impact."

“Then let’s pray we don’t encounter a thunderstorm,” Susan said, sitting down. “Or that something strange will emerge from the sea.”

"Don't worry." Chen Hao leaned against the railing. "The scariest thing about this kind of place is that there are a lot of fish and the waves are a bit big. It's not like a dragon king is going to jump out."

The moment the words were spoken, the ship suddenly shuddered.

It wasn't the kind of shaking caused by wind and waves. It was more like the bottom had hit something.

All four of them stood up.

"What's going on?" Susan asked, gripping the handrail.

Nana quickly pulled up the bottom scan image. The screen showed an irregular shadow beneath the hull, its shape neither like a reef nor like shipwreck debris.

“There’s something down there,” she said.

"How big?" Chen Hao leaned closer to take a look.

“Approximately three meters in diameter, height unknown,” Nana continued her analysis. “The material is unidentifiable, and the reflected signal is abnormal.”

"How abnormal is it?" Carl asked.

“It’s not like metal, nor like rock,” she said. “And…it’s moving.”

"Move?" Susan's voice rose slightly. "Follow us?"

“No,” Nana shook her head. “It crossed from the starboard side, and it was faster than the ship.”

Chen Hao stared at the screen; the shadow had moved out of the detection range.

"Was that jolt just now caused by it grazing past?" he asked.

“The probability is very high,” Nana said. “The closest distance was less than two meters.”

The cabin was quiet for a few seconds.

"So we almost got knocked over by something we didn't recognize?" Carl chuckled wryly. "This trip back was really a steal."

“Perhaps it’s just a coincidence,” Susan said. “There are all sorts of geological activities on the seabed.”

“But it moves,” Nana added, “and its trajectory isn’t random.”

Chen Hao scratched his head. "Whatever it was, at least we didn't crash. Let's keep going and not scare ourselves."

The ship continued its journey, the engine humming steadily. The sky remained overcast, but the wind had subsided slightly. Nana entered low-power mode, her blue eyes flashing at a slow frequency, and she sat motionless in the corner.

Susan stared at the navigation chart, glancing up at the sea every now and then. Carl rested with his eyes closed, but his brow remained furrowed. Chen Hao stood at the bow, his hand on the railing, watching the waves being cleaved open ahead.

Two hours later, the alarm went off.

It wasn't an engine malfunction, nor an electrical problem. It was a short beep from the navigation system.

Nana immediately opened her eyes, and the blue light flashed faster. She rushed to the control panel and brought up the signal source.

"I received an encrypted signal," she said. "The frequency is unusual, and the transmission method is unknown."

"Where did you come from?" Chen Hao turned around.

“The direction comes from the seabed,” she said. “The depth is over 1,500 meters.”

"That thing again?" Susan stood up.

“Uncertain.” Nana quickly operated the system, “but the information it’s sending… is attempting to access our database.”

"What database?"

“Backup data from the research station,” she said. “It’s requesting access.”

Chen Hao stared at her. "Can you refuse?"

“The connection can be cut off,” she said, “but once disconnected, it could trigger reverse tracing.”

“Then don’t break it,” Chen Hao said. “Let it continue.”

"Are you crazy?" Karl opened his eyes. "Who knows who this is? What if it's a virus program that takes control of our ship?"

“The problem is,” Chen Hao said, looking at the screen, “that it’s already connected.”

Nana's finger hovered over the last confirmation button. Her blue-eyed gaze was fixed on a certain number.

"The signal content has begun to be transmitted," she said. "The first segment of data has been received."

"What is it?" Susan asked.

Nana was silent for a second.

“It’s coordinates,” she said. “A set of latitude and longitude coordinates, labeled ‘node b’.”

Chen Hao narrowed his eyes. "A node? Isn't there only one research station?"

“There were originally four.” Nana pulled up the map. “We know two now. This signal comes from the third one.”

The wind and waves outside the ship grew stronger, and the seawater deepened in color. In the distance, a bolt of lightning streaked across the sky, illuminating half of the sea.

Chen Hao walked to the control panel and stared at the coordinates.

“Since it proactively sent the message,” he said, “it means—someone doesn’t want us to be completely kept in the dark.”