The page had not merely disappeared. Someone had replaced it.
Wei stood in the subway entrance while commuters pushed around them. The first version of the revision list showed seven pages. The new one showed six, and the document history named Ye Xuan as its editor.
“Can you open the old version?” Ye Xuan asked.
“Maybe. But I don’t want to touch anything.”
“Then don’t. Photograph what you can see now.”
Wei took screenshots of the file details and the revision time. Ye Xuan did the same. He resisted the urge to sign in and investigate.
“If someone used your account, change your password,” Wei said.
“After we preserve this. The institute needs to check its sessions.”
“Are you saying somebody stole your account?”
“I’m saying the log doesn’t prove I edited the document.”
Wei stared at him. “That sounds like something Mara would say.”
They called the institute’s technology desk. The employee who answered gave them a case number and arranged for the account sessions to be reviewed. Ye Xuan changed his password through the official recovery page, without deleting files or existing records.
Whatever had happened at the waterfront, he would not let an unknown person continue speaking in his name.
“We should call Reed,” Wei said.
Ye Xuan already had the detective’s card in his hand.
Reed listened without interrupting. When Ye Xuan finished, she requested the screenshots and the university case number.
“Do not try to identify the user yourselves,” she said. “A name in an edit history tells us which account was used, not who was sitting at the keyboard.”
“We know,” Ye Xuan answered.
“You know it now. Keep knowing it tomorrow.”
At the institute they met Dr. Helen Price, the lecturer supervising the observation placement. She wore a navy sweater with the sleeves pushed above her wrists and looked as if her research had been interrupted by another person’s emergency.
“Mara Chen wanted students who could document changes independently,” she said. “I thought that was a sensible exercise.”
“Why did she ask for older drawings?” Wei asked.
“Because a completion report referred to a revision I couldn’t find.”
Price took a folder from a locked cabinet. Inside was the original assignment packet, bearing the institute’s receiving stamp. She confirmed the students’ authorization before opening it.
The seventh page was a schedule of inspection exceptions.
Ye Xuan read it carefully. Two unresolved items were listed: an unverified pipe alignment and a service access passage absent from the latest plan.
Beside each item was a box for the person responsible for closing it. Both boxes were empty.
“That’s what went missing,” Wei whispered.
“From your shared folder,” Price corrected. “We still have this paper copy.”
Ye Xuan studied the attached drawing. Its symbols were familiar now, but there was a new notation: a dashed line running behind the wall, ending at a rectangle marked ACCESS BY SEPARATE PERMIT.
“Where does that lead?” he asked.
“I don’t know,” Price said. “We’d need the original survey.”
“Could it be a maintenance crawlspace?”
“Possibly. Or it could be a drawing convention used by the contractor.”
Mara had not necessarily discovered some hidden chamber. She had been asking whether work had been inspected before someone declared it finished.
That made her disappearance no less alarming.
Price agreed to supply the packet through the inquiry channel. Ye Xuan requested only the pages he was already authorized to use. He didn’t want to carry records that belonged to other people’s jobs.
Outside, Wei finally breathed.
“They had the page all along.”
“A different copy,” Ye Xuan said. “The question is why someone changed ours.”
The institute’s security desk called before they reached the stairs. The account had been accessed through a session token issued to a workstation in the student engineering lab. No one could yet say who used the workstation or whether the token had been copied.
Wei stopped walking.
“We used that computer on Tuesday.”
“Then tell them.”
“I did.” His face had turned pale. “I left my bag there when I went home.”
“A forgotten bag isn’t a confession.”
Wei gave a short laugh.
Across the atrium, people applauded an Awakened responder who had straightened a bent steel rod with two fingers. A lecturer explained that the demonstration was licensed and the rod inspected for damage.
Ye Xuan thought of the missing signatures. Nobody applauded the work required to establish whether a wall was safe.
His phone buzzed with Reed’s reply. The packet had been received. An investigator would request the relevant access records.
A second message followed from an unknown sender.
There was no threat. Only a photograph.
It showed the steel ruler against the wet seam, the same scene as on Ye Xuan’s phone, but from farther away. A woman with an orange equipment case stood beside the wall.
Behind her, a narrow service door stood open.
Ye Xuan enlarged the image. Darkness filled the opening.
Under the photograph were four words.
She went in alone.