Siheyuan (traditional courtyard house): Starting with the Korean War, returning home to take charge

When Lao Sun entered, He Yuzhu was flipping through the rocket launcher test report. The numbers were dense, making his eyes sore. He took off his glasses and rubbed his nose. Lao Sun hadn't knocked before coming in, something that had never happened before. He Yuzhu looked up and saw that Lao Sun's complexion wasn't good, and he was holding a brown paper bag in his hand, not putting it on the table, just clutching it.

"Zhao Desheng spoke up again."

Old Sun placed the paper bag on the corner of the table, but didn't sit down. He walked to the window and stood there. The sky outside was overcast, and the wind made the big-character posters on the courtyard wall rustle, the edges of the paper curling up and then falling back down. He lit a cigarette, took a puff, and the smoke spilled from the corner of his mouth, stuck to the glass, and slowly dispersed.

"He said that Pu Zheng entered the country once in 1968. He came from Myanmar, taking the Ruili route."

He Yuzhu's hand stopped on the report. He looked at Lao Sun's back, waiting for him to continue.

Old Sun turned around, held the cigarette between his fingers, and didn't smoke it anymore. "I stayed in Kunming for three days. I met five people. Then I crossed the border and went back to Hong Kong."

He Yuzhu didn't speak. He lowered his head, looking at the report on the table. The numbers were still there, but he couldn't focus on them anymore. Pu Zheng entered the country. The old man with gold-rimmed glasses, wearing a dark suit, standing in front of the small Western-style house in Hong Kong, had been to the mainland. In 1968, before Zhenbao Island. He came from Myanmar, taking the Ruili route, with someone to meet him and someone to cover him. He stayed in Kunming for three days, met five people, and then swaggered across the border.

"He dared to enter the country."

He Yuzhu's voice wasn't loud, as if he were talking to himself. Old Sun didn't reply, but stubbed out his cigarette on the windowsill, the ashes falling and drifting to the ground.

"Zhao Desheng only remembered three. A deputy director surnamed Liu in the Logistics Department of the Kunming Military Region. A deputy director surnamed Li in the Provincial Supply and Marketing Cooperative. A professor surnamed Zhou in the Physics Department of Yunnan University."

Old Sun pulled a piece of paper from the paper bag and placed it on the table. The paper contained a few lines of handwritten text, the handwriting messy, but the workplace and position were clearly written. He Yuzhu picked it up, glanced at it once, and put it down. Then he picked it up again and looked at it a second time.

"Investigate. Find out everyone he's met within the country. Leave no one out."

Old Sun nodded and left. His footsteps faded into the distance in the corridor. He Yuzhu sat at his desk and looked at the names again. Kunming Military Region Logistics Department. Provincial Supply and Marketing Cooperative. Yunnan University Physics Department. Physics Department. He stared at those three words, his fingers tapping unconsciously on the table. Why was Pu Zheng looking for a physics professor? He remembered Zhou Weixian working at the research institute for five years, filling up genetic data. Now another physics professor had appeared. These people's reach was quite far.

Three days later, Old Sun called. He Yuzhu answered, and the voice on the other end was very low, as if afraid of being overheard.

"We found out in Kunming. The deputy director surnamed Liu has retired and is in Kunming. People from the provincial department contacted him, and he confessed. Pu Zheng asked him about troop movements. He didn't say anything, but he took money. The deputy director surnamed Li has also retired and is in his hometown. Pu Zheng asked him about material reserves. He also took money."

He Yuzhu held the microphone but didn't speak. Old Sun paused for a moment, then continued, "The most troublesome one is that professor. Professor Zhou, he's still employed. People from the provincial department went to him, and he said he didn't know anything about Pu Zheng and had never met him. But Zhao Desheng insists he did."

"Bring him back. I'll interrogate him."

Old Sun said, "Okay."

It was already dark when Professor Zhou was brought to Beijing. He Yuzhu stood outside the interrogation room, watching him through the glass. Professor Zhou was in his sixties, thin, wearing reading glasses and a faded blue cotton jacket with frayed cuffs. He sat in a chair with a glass of water in front of him, untouched. His hands rested on his knees, his knuckles white.

Old Sun went in and sat down opposite him.

"Professor Zhou, do you know why we invited you here?"

Professor Zhou looked up at Old Sun, his gaze calm. "I don't know. I'm a physicist; I haven't broken the law."

Old Sun pulled a photo from the folder and pushed it in front of Professor Zhou. In the photo, Pu Zheng was standing in front of that small Western-style building in Hong Kong, wearing gold-rimmed glasses, a dark suit, and his hair was neatly combed. Professor Zhou glanced down at it, his expression unchanged, but his fingers curled slightly on his knees.

"Never seen it before."

Old Sun stared at him. "Professor Zhou, in 1968, Pu Zheng stayed in Kunming for three days. Zhao Desheng told me that you met at the Cuihu Hotel and had tea for an hour."

Professor Zhou gripped his trouser leg tightly. He didn't look up, his voice remaining relatively steady. "Who is Zhao Desheng? I don't know him."

Old Sun stood up and walked to his side. "Zhao Desheng is a Manchu remnant; he's been arrested. He's implicated many people, including you."

Professor Zhou's shoulders twitched. The room fell silent, save for the crackling of the emergency exit lights in the corridor. After a long while, he looked up, his eyes reddening.

"I...I didn't know he was a spy. He said he was a businessman and wanted to learn about some things in physics. I..." He paused, his Adam's apple bobbing. "I said some things. I thought it was just common sense."

He Yuzhu pushed open the door and sat down opposite him. "What did you say?"

Professor Zhou looked at He Yuzhu, his lips trembling. "The critical mass of uranium. The purification process of plutonium. The design principle of the hydrogen bomb."

He Yuzhu placed his hand on the table. He looked at that thin face, those reading glasses, those reddened eyes. A university professor, who had taught for half his life and nurtured countless students. Pu Zheng offered him a cup of tea, and he revealed the secrets of nuclear weapons.

"What benefits did he give you?"

Professor Zhou's tears streamed down his face. "No. He said he just wanted to understand. I... I didn't expect it to turn out like this."

He Yuzhu stood up and walked out of the interrogation room. One of the lights in the corridor was broken, and the green light from the emergency exit illuminated the floor. He stood there, listening to Professor Zhou's sobs inside, each one suppressed, as if squeezed out from his throat.

That evening, He Yuzhu sat alone in his office. He took the list out of his drawer and turned to Pu Zheng's page. After the words "Prince," he added a few lines: "Secretly entered Kunming in 1968, met with five people. Three have been verified: Deputy Director Liu (Military Logistics), Deputy Director Li (Provincial Supply and Marketing Cooperative), and Professor Zhou (Yunnan University Physics Department). Zhou confessed to leaking nuclear weapons principles."

He finished writing, put the list back, and locked the drawer. He stood up and walked to the window. The moon was bright outside, shining on the courtyard wall, casting patches of shadow on the ground from the posters. He remembered the photograph of Pu Zheng, remembering him standing in front of that small Western-style house in Hong Kong, his hair neatly combed, like a respectable businessman. He had been here, stayed in hotels in Kunming, drunk tea at the Cuihu Hotel, and met those people. Then he crossed the border and returned to Hong Kong.

They can come and go as they please.

He stood there for a long time before drawing the curtains.