The sound of the fork falling into the plate still echoed in Chen Hao's ears, but he didn't pick it up.

He stared at the message Carl had brought—the signal had returned from the seabed, lasting thirty-seven seconds, exactly the same as the first time. It was six hours after they left. It was as if someone had pressed play down below.

“It knew we were gone,” Susan said.

“It could also be an automatic loop,” Carl said, arms crossed. “Like a broken refrigerator that keeps making noise.”

Nana stood in the corner, the indicator light flashing rapidly: "The signal source location has shifted by 0.3 kilometers, heading towards the inside of the deep-sea cliff. There is an 82% probability that it is not a fixed device."

Chen Hao stood up, causing his chair to slide back a bit. He ignored it and simply said, "Prepare for the next sea voyage."

No one asked why. Last time, they brought back data, samples, and a piece of metal they couldn't understand. This time, the signal returned on its own, as if urging them on.

The projector in the conference room was still on, and the structural diagram of the secret room was still hanging on the wall. Chen Hao walked over and traced the location of the door with his finger.

“We’re dressed too poorly,” he said. “Next time we go down, we can’t rely on luck to open the door; we have to rely on our equipment to force our way in.”

The laboratory lights were on early the next morning.

Nana had already retrieved the deep-sea environmental parameters from the database. High pressure, low temperature, strong magnetic field, and corrosive water were all listed on the screen. She began simulating the structural model of a new diving suit.

"The outer layer needs to be made of pressure-resistant material, the middle layer needs to be an electromagnetic shielding layer, and the inner lining needs to be temperature-regulating," she said. "The oxygen supply system needs to be modular and detachable to avoid single points of failure."

“Sounds like a spacesuit,” Susan said, flipping through her notes. “But we’re in the ocean, not on another planet.”

“The logic is the same,” Nana said. “They are both extreme environments.”

Carl squatted down to inspect the circuit board of an old probe: "The current diving suits can't withstand depths below 7,000 meters. The seams are prone to cracking, and the helmet visor deforms slightly under high pressure, making things blurry. I wanted to fix it when I came back last time, but I haven't gotten around to it yet."

"Let's get started now." Chen Hao came in from outside, carrying a toolbox. "I just searched the warehouse, and all the stock materials are no good. Titanium alloy is barely enough, but it's too heavy and inconvenient to move around in. We need something light, strong, and corrosion-resistant."

"You have an idea?" Susan looked up.

“No.” Chen Hao put down the box. “So I’m going to go out and look for it.”

Three days later, Chen Hao drove a small exploration boat alone down to the edge of a cliff five kilometers away from the site of the previous secret chamber.

The terrain in this area is complex, with steep cliffs and unstable water flow. He used a robotic arm equipped with a portable drilling machine to take samples from several exposed rock strata. The first two samples were so ordinary that analysis was unnecessary.

The drill got stuck for the third time.

"Damn." He glanced at the pressure gauge, adjusted the angle, and tried again. This time, when it retracted, the robotic arm caught a piece of debris the size of a fingernail.

It's a dark silver color with a non-reflective surface, but it feels unusually smooth to the touch. The strangest thing is that when it's attached to the metal clamp of the robotic arm, it makes a slight "click" sound, like two magnets sticking together.

Chen Hao put it into the sealed compartment and turned on the portable detector.

He paused for a moment when the density reading popped up.

“This thing weighs twice as much as lead, but it doesn’t look heavy at all,” he said into the communicator. “Can you check if there’s any metal that won’t rust even after being submerged in seawater for three years?”

Nana's voice came quickly: "There are no matching items among the common metals on Earth. We recommend returning to space immediately and having the samples analyzed in the laboratory."

“Okay.” Chen Hao put the sample away. “But I have to say—this doesn’t look like it was formed naturally.”

Back at the base, the four of them gathered around the experimental table.

Susan put on gloves and placed the fragment on the testing table. Carl turned on the spectrometer; the waveform on the screen flickered a few times and then stopped.

“The ingredients are unknown,” he said. “There’s no record of it in the database.”

“Let’s name it,” Nana said.

“X-7,” Chen Hao blurted out. “Sounds like a failed model, but it’s suitable for us.”

Nana accessed the database and began comparisons. Thousands of known metals were eliminated one by one. The final conclusion showed that the substance was not in the existing material list.

“This is the first discovery,” she said. “It is recommended to list it as a high-priority research subject.”

"Test the strength first." Carl brought over a pressure testing machine. "Let's see how much it can withstand."

The machine started up, and the readings climbed steadily. At 1,000 atmospheres, the X-7 showed almost no deformation. At 1,100 atmospheres, the instrument alarmed, indicating that it had reached its limit load.

“The titanium alloy would have collapsed under this pressure long ago,” Susan said, looking at the data. “Its stability is outrageous.”

“And this too.” Nana placed a small piece of X-7 into the electromagnetic interference zone. Ordinary metals immediately caused equipment fluctuations, but this material was as if it didn’t exist; the surrounding magnetic field remained completely still.

"It has strong anti-interference capabilities," she said. "It can be used in shielding systems."

Chen Hao picked up the fragment and examined it against the light. It didn't reflect light, nor did it absorb heat; he couldn't even feel any temperature change when holding it in his hand.

“Our new diving suits will have this as the outer shell,” he said. “The helmet, joints, oxygen tank cover—it’ll cover everything. If anyone dares to say we don’t look like futuristic warriors, I’ll hit them on the head with this thing.”

“There aren’t enough materials,” Susan warned. “We only have this small piece; we can’t make a complete set of equipment.”

“Then let’s go dig some more.” Chen Hao put the fragments back into the container. “If we can find them even on the edge of a cliff, it means there’s a mineral vein underneath. We don’t need too many; let’s make a prototype first.”

“What about the risks?” Carl asked. “What if this thing is radioactive, or releases toxins when it comes into contact with water?”

“Toxicity testing is already underway,” Nana said. “Preliminary results show good biocompatibility and no harmful elements have been released.”

“Then it’s usable.” Chen Hao made the decision. “The design drawings will be ready tonight, and construction will begin tomorrow.”

That evening, Nana drew the first draft of the diving suit in the lab.

Three-layer structure: inner layer of temperature-controlled gel, middle layer of X-7 alloy mesh skeleton, and outer layer of flexible protective membrane. The helmet features a spherical visor and a built-in micro oxygen circulation system. Two replaceable oxygen modules are mounted on the back, and tool slots are added to the sides.

“It can be even lighter,” she said. “If we make the X-7 with a honeycomb structure, the strength remains the same, but the weight can be reduced by 15 percent.”

"It sounds like helping an overweight person lose weight," Chen Hao said, leaning over the table. "But I support it."

Susan suggested installing biosensors: "They can monitor heart rate, blood pressure, and blood oxygen levels, and automatically trigger an alarm if anything is abnormal."

"Don't make it like a hospital," Chen Hao waved his hand. "But we can add a urine bag. It's not easy to go down there, you can't come back holding it in."

Carl was in charge of the circuitry. He removed the miniature camera from the detector, intending to mount it on top of his helmet. "At least that way I can see if there are any craters under my feet."

At 3 a.m., the design was finalized.

Chen Hao stood up, yawning. "Tomorrow I'll apply for an exploration permit and take the drilling rig down to collect more material. Which of you three wants to come with me?"

“Me,” Susan said, closing her notebook, “I want to see for myself if there really is a mine there.”

“Count me in.” Carl tightened the last screw. “I’ll only feel at ease if I install the new equipment myself.”

Nana stood in front of the terminal, uploading design files: "I will remotely monitor all data streams and update the emergency plan in sync."

"Okay." Chen Hao stretched. "This time, we're not just going to find something, we're going to build ourselves wings."

The exploration vessel set sail again at noon the next day.

Wearing an old-fashioned diving suit and carrying a modified oxygen tank, along with a drilling rig and sampling bags, Chen Hao slowly descended along the edge of the cliff. Susan monitored vital signs on the boat, Carl adjusted the newly installed communication repeater, and Nana constantly adjusted the detection frequency to help them avoid areas with strong magnetic fields.

Upon reaching the target location, Chen Hao used the robotic arm to clear the rock crevices. The samples he had drilled in the previous times were all quite ordinary. Until, deep within a crack, he saw a dark silver reflection.

He leaned closer and gently pried it open with a scraper.

A piece of ore the size of a palm fell off and slowly floated up.

He reached out to grab it, and the ore suddenly trembled slightly, as if it had sensed something.

The moment his glove touched the surface, the entire rock instantly became scorching hot.