Han Rui covered the labels on three plots with strips of paper and turned the laptop toward Yanchuan.
“Which one would you approve?”
They were alone in a workshop meeting room outside Shenzhen. The company had permitted Han to show a set of anonymized demonstration records from its own equipment. Nothing had been copied from the installation in Kenya. The profiles were similar enough to make the question useful and different enough to prevent Yanchuan from calling the answer a reconstruction.
“Approve for what?” he asked.
Han sat back.
“Good. You’re learning.”
Two weeks earlier Yanchuan would have been annoyed by the little examination. This morning he was grateful for a question whose answer did not depend on anyone being missing.
The first plot showed electrical output stabilizing under changing demand. The second showed a longer unsettled interval before reaching much the same output. The third had the smoothest line of all, with a note that auxiliary loads had been excluded from the calculation. He could identify the reporting choices. He could not say whether any of them met a contract he had not seen.
Mei arrived with a bag of steamed buns and asked Han to remove the labels from the time axes as well.
“Why?” Yanchuan said.
“You keep recognizing the shape you’re hoping to find.”
She was right. Every interruption had begun to resemble the fourteen minutes in his brother’s archive.
Han gave them the test conditions only after they had written what each plot established. They worked through the calculation twice: once using the settled operating interval, and again including the measured auxiliary demand. Both answers were arithmetically sound. Only one described the total load the second question had asked about.
“That’s the problem in Kenya,” Yanchuan said.
“It’s a possible reporting mechanism,” Mei corrected. “These are not their measurements.”
“I know.”
“Then don’t put their site name on our chart.”
He removed it from the draft heading. Under limitations he wrote that the exercise demonstrated sensitivity to the selected load boundary; it neither reproduced the overseas test nor established intent.
Han read the sentence and pointed at sensitivity.
“People paying the bill won’t know what you mean.”
Yanchuan replaced it with a shorter explanation: changing which loads are counted can change whether the reported performance meets the target, even when the instruments are working correctly.
It had taken them most of a morning to say that honestly.
No manager had stood behind them. There was no camera trained on the display, no audience to applaud a number turning green. The result could be checked by another engineer with the same files. That was what Yanchuan wanted from it, though he wished the finding were less ordinary.
At lunch Amina called from Kenya. She had obtained permission for a limited record review by the operator’s maintenance engineer and the contractor’s designated reviewer. No equipment would be switched for the family’s benefit. They would compare the October ticket, the handover requirement, and the retained event record in a room where each organization could identify what it had supplied.
“I thought they were going to repeat the test,” he said.
“We already witnessed a demonstration,” she replied. “You saw what happened when the load changed. Now they need to explain the earlier record.”
“Who’s attending?”
“People who are authorized to make a technical finding. Not you, not me as your guide, and not an invited audience.”
He almost objected to being left out. Then she told him the operator had asked whether his independent comparison could be supplied as a statement of method, with its limits intact.
He sent it through the review channel. Mei made him remove an illustration borrowed from a training manual because they had no right to redistribute it. Han signed the page describing the workshop’s conditions and refused to sign a conclusion about another site.
The following Wednesday Yanchuan returned to his own work. Chen had assigned him a client’s cooling reserve calculation that had fallen behind while he was traveling. A draft optimization system suggested reducing a reserve because historical demand had never reached it. In the small print, its demand history excluded emergency exercises.
He restored the exercises as a separate scenario. The recommendation became less impressive. The client would have to choose which promise it needed to keep.
Chen read the two figures.
“Can they afford the larger reserve?”
“I haven’t calculated that yet.”
“Then do it. A warning without a price is only half a recommendation.”
Yanchuan finished the estimate before checking his personal phone. For a few hours he had been an engineer whose work was not an instrument of the search. He felt both lighter and ashamed of feeling lighter.
The overseas review’s first note arrived that evening. The original ticket described an auxiliary cooling change as temporary, pending a restoration check. The document controller’s copy of the acceptance package treated that load as outside the final comparison. The reviewers could not find an authorized change to the acceptance scope among the records then available.
One entry in the work-management system said the temporary arrangement had been closed. The closure was associated with a document transfer. It did not identify a technician who had checked the physical arrangement afterward.
Yanchuan read that line three times. It was tempting to call it proof that the cooling change had remained in place.
Amina was still on the call.
“Please say what you’re thinking.”
“Someone closed a work item without showing that the work was done.”
“They closed an item without a restoration record we can locate. There might be one elsewhere.”
“Do you think there is?”
“I think the next question is who would have made it.”
He added that question to the document. In another column he asked who had permission to close the ticket, and whether the closure was an administrative transfer or a sign-off for the physical work.
An joined the call from Guangzhou. Their son had spilled soup on a school worksheet and was trying to dry it with a hairdryer. She muted herself briefly to stop him from scorching the page.
When she returned, Yanchuan explained the new review in three sentences. She asked who had the originals, who would retain the response, and whether the finding could be shared with the missing-person investigator. He had answers to all three. Their process had begun to work even when he was not directing it.
“Does it help find him?” she asked.
“Not yet.”
“All right. Keep the distinction.”
Afterward he sat alone with the three anonymous plots from Han’s workshop. One was smooth because the system had been measured under gentle conditions. One was untidy because the transition was shown. The third was reassuring because a boundary had been drawn around what counted.
He closed them and opened the photograph of Yansheng beside the packing crate. His brother had once made a manager check every mislabeled part, even when the first correction seemed to settle the problem.
The review had not proved a crime. It had shown a technical question that deserved a complete answer and a handover that still lacked a named witness.
Han had written the test conditions along the edge of the plots in pencil. Yanchuan kept the marked copy, not the cleaner one prepared for presentation.
On his desk, beside the photograph, the case chronology remained open to Friday, October 30. The visitor’s departure column was blank in the copy the family had received. Tomorrow Wanjiru expected an answer about that blank.
Yanchuan saved his calculations without opening the next message early.