I started with a ship full of max-level veterans, and I'm just a complete noob.

The unsealing knife moved slowly along the edge of the oil paper, separating the brittle fibers with the tip. Chen Ke watched Jiang Ming's hand, his chest rising and falling with the movement, as if waiting for a judgment that was many years overdue.

Without damaging the sealing wax, Jiang Ming first cut open the outer layer of oil paper from the side, and then pulled out the neatly folded old document bag inside.

The document bag had turned yellow, and a piece of dark red sealing wax remained on the seal. Fragments of wax had fallen from the edge onto the white gloves. Director Wang asked Li Da to bring a magnifying glass and an evidence tray, and then moved the teacup on the table to a distance.

Jiang Ming pulled a letter from the file bag.

The paper was thin and stiff, with undulations along the edges caused by long-term dampness, and several dark stains. There was no title at the top, and the entire page was written in English, with dense formulas crammed between the lines, and a graph showing the relationship between speed, frequency, and echo delay drawn next to it.

Jiang Ming placed the first card on the table, then the second card was placed on the right side, and the third card covered the gap in the middle.

Those symbols, strung together across the pages, formed a set of early pulse Doppler radar system concepts. Transmit pulses, echo windows, target velocities, and clutter frequency shifts were arranged in the same logical framework, and even the then-rudimentary filtering process was written out with a path that could be converted for engineering purposes.

Chen Ke didn't approach, only asking, "Can you understand it?"

"I can understand part of it."

Jiang Ming marked three symbols on the edge of the paper with a pencil, without touching the ink with his fingertips.

"This is not a private letter; it contains no personal information. The deduction starts from the first line, which mentions the radar system."

Director Wang took the comparison materials handed over by Li Da, placed the papers preserved in the old case under the light, and compared the fiber texture, horizontal indentation, and edge cutting methods of the two types of paper one by one.

Li Da used tweezers to pick up the old paper, aligned it with the edges of the letter, and whispered, "The batches are the same, and the cutting edges are consistent. The few pages of tattered manuscript in the old case and this batch of paper came from the same batch."

Director Wang did not rush to a conclusion, but only wrote down the paper number and comparison results on the record sheet, and then looked at Jiang Ming.

Jiang Ming continued reading.

Lei Zhenbang wrote several English abbreviations next to the diagram, one of which corresponded to Qian Xuesen and the other to Guo Yonghuai. There were also unfinished annotations after the names, indicating that this concept was once intended to be submitted to domestic researchers responsible for aerodynamics and overall design for discussion.

Jiang Ming reassembled the letter, his gaze moving downwards along the curve left by Lei Zhenbang. When he read a passage about speed changes and echo phase differences, the time coordinates from ten years ago appeared in his mind.

At the time, Lei Zhenbang lacked mature high-speed devices, as well as sufficiently stable pulse sources and measurement equipment, but he was already trying to establish a theoretical foundation for air defense radar for the new China.

This piece of paper has been preserved to this day, and the derivations on it still point to the same problem: how to distinguish a real moving target from complex clutter.

Jiang Ming's throat was dry. He readjusted the position of the letter to prevent the sheets from shifting due to the tilt of the table.

He thought of the high-frequency silicon tube that had just been completed in Laboratory 502, the short frame pulses sent back from Aksai Station 3, and the equipment and teams that Lei Zhenbang would never see. The paper in his hand suddenly felt heavy.

Chen Ke watched his movements and finally spoke: "Back then, people from Mr. Deng's system came to Lei Zhenbang. They knew the importance of these manuscripts and that they contained an early approach to dealing with airborne radar."

Director Wang looked up: "You saw them with your own eyes?"

"I've met two of them and overheard their conversation." Chen Ke tapped his fingers lightly on his knee a few times. "They wanted Lei Zhenbang to hand over the manuscript, saying that research results should be managed centrally and that individuals had no right to keep them privately. Lei Zhenbang did not agree."

"What happened next?"

"He disassembled the manuscript and hid it in several different places. He also copied the most crucial derivations into English, intending to send them back to China through overseas academic correspondence." Chen Ke looked at the table. "After they discovered this, they began to interrogate him about the whereabouts of the manuscript, but he did not hand it over."

Chen Ke did not continue to describe the details of Lei Zhenbang's ordeal, and Jiang Ming did not press for further information.

The deaths, stigma, and journeys to the Northwest in the old case had already been pieced together by the fragments from the previous text. The letter that appeared today merely added a piece of technical background that had been deliberately torn out on that outline.

Comrade Song, who was by the window, suddenly raised his hand.

Jiang Ming followed his gaze and saw two people standing at the entrance of the alley at the end of the street across the street. One was wearing a gray cloth jacket and the other was wearing an old hat. Neither of them was taking shelter from the rain, but their heads were turned towards the second floor of the guesthouse.

One of them raised his hand to his ear, as if checking the lights upstairs.

Comrade Song did not speak, but tapped his finger on the window frame, then stepped back to the wall and gestured to Director Wang.

Director Wang immediately took out his walkie-talkie, turned around, and walked to the door.

"Group Two at the front gate, pay attention to the alley entrance; Group Three at the back alley, block off the electrical box location. When taking action, first control the people, preserve the objects at the scene, and prevent the targets from coming into contact with each other."

After the order was given, footsteps sounded downstairs first, but the hawking noises on the street still drowned out most of the noise. Only the sound of a drawer being pulled open came from the first floor of the guesthouse, followed by the sound of chairs being moved and a brief argument.

Chen Ke reached his hand towards the edge of the table, but Jiang Ming pressed his wrist down.

"We haven't collected everything yet, don't touch anything."

Chen Ke looked at Jiang Ming, his expression even more somber than before.

"They will definitely follow me after I show up this time."

"You knew there were people watching, yet you still chose to wait for me here."

"Because this manuscript can no longer go through the original channels," Chen Ke said. "I don't know who can still access the old archives, nor do I know who will send the message out. Only by handing it to you personally can I dare to tell you what happened next."

The sound of pulling came from downstairs, the wooden planks were banged and rattled, and Li Da's voice came from the stairwell.

"Director Wang, we've caught two people. One was carrying thin iron pliers, and the other was wearing insulating cloth. They were dismantling the electrical distribution box, as if they were preparing to cut off the power to the guesthouse."

Comrade Song walked to the door and looked down to make sure Li Da had the two under control before turning back to close the door.

Jiang Ming put the letters into the waterproof bag in their original order, then put them into another document bag. Director Wang stamped a temporary number on the seal, and Li Da was responsible for taking photos to record the placement of each piece of paper.

"This manuscript will be handed over to the security department for safekeeping," Director Wang said.

Jiang Ming looked up at him: "I will take the original back to 502. The security department will keep the images and archive the records."

Director Wang looked at him for a while, but did not agree immediately.

Jiang Ming put the waterproof bag into his inner pocket and pressed the opening shut with his palm.

"Aksai Station No. 3 has received short frame signals from the enemy's airborne radar. The existing receivers can only preserve part of the waveform. Lei Zhenbang's concept can at least help us determine how the enemy gets rid of ground clutter from the velocity echo. If the components leave the technical site, the conversion speed will be much slower."

Director Wang knew about the intelligence he possessed regarding Aksai, but he was unaware of the deep connection between the letter and the enemy's radar. Jiang Ming also refrained from presenting his unverified assessment as a conclusion.

"I will have Comrade Song oversee the entire process, keeping the original documents with me at all times, and making records of all technical usage."

Director Wang looked at Chen Ke: "You should move first. The location will be arranged by the security department."

Chen Ke stood up, put the pen back in its inner pocket, picked up the half-empty cup of tea, but didn't finish it.

"Lei Zhenbang once said that a true air defense network cannot rely on just one machine; it must ensure that every echo is recorded and verified at different locations and times."

Upon hearing this, Jiang Ming pressed his fingers against the outside of his pocket.

Director Wang instructed Li Da to go downstairs and clear the way, while Comrade Song was responsible for escorting him closely. Chen Ke was then transferred through the back door by two security personnel.

The two people arrested downstairs were taken away separately. Next to the electrical box, there were pried-open screws and a piece of cut copper wire. Rainwater flowed down the wall, blurring the footprints on the ground.

Jiang Ming was the last to leave the room, glancing back at the table.

The two teacups were still there, but the tea had gone cold. The scraps of oil paper from the old document bag were put into the evidence bag, and the fountain pen left by Chen Ke was temporarily registered by Director Wang.

The unlicensed jeep on the street corner started up again, and Chen Ke was seated in the middle vehicle. After the curtains were drawn, the convoy split into two groups and drove away from the guesthouse.

Jiang Ming got into the car, his hand still pressed against the waterproof bag.

The car wheels rolled through the puddles, and the lights from the back alley of the guesthouse flashed past the car window. Lei Zhenbang's severed theoretical clues had returned to reality, and the enemy aircraft radar at the Aksai front had thus gained another technical path to trace.