They maintained this position for several long and unpleasant minutes while a few of the soldiers crawled toward each other and conferred. Then a command was barked and all but two of the Russians stood and slung their rifles.

"Can we move now?" Chang asked.

"No; we are still in danger."

Two Russians walked across the plaza toward them. Some meters distant, they stopped. "Do you speak Russian?" one asked, in Russian.

"I do," Chang replied in kind. "My English is better."

"My terrible English," the spokesman said, demonstrating his point. "You are Chinese?"

"Yes. We were on a walk," Chang said. From this point on, they spoke Russian.

"I am Corporal Rodzhensky, and this is Corporal Fremov. Something has gone wrong in the library; we are not sure what. We cannot allow anyone to pass; besides, the building is closed and will not open for us."

"Do you have any idea what the trouble is?" Chang asked, struggling to appear especially interested and polite.

"No. We heard gunfire, and then the black. . . wall closed, and would not open."

"Why was there gunfire?"

"We do not know," Rodzhensky said, glancing nervously at Fremov. "We have communicated with our superiors in the fourth chamber, but they have not arrived yet."

"We will help any way we can," Chang said. "Or, if you wish, we will leave."

"No. . . Perhaps you can approach the door, try to make it open. It may be ridiculous, but then again. . .” Rodzhensky shrugged, then suddenly realized guns were still being trained on the pair. "Do you have weapons?" he asked, looking over his shoulder at the prone riflemen.

"No. We are scientists."

Rodzhensky called out for the riflemen to put away their guns. "We are not familiar with this place," he said. "It makes us nervous. Especially now. Our officers are inside that building—searching for a fugitive." He frowned and seemed to realize he was revealing too much to outsiders. "Please, come with us and see if the door will open for you."

Chang explained what had happened to Wu, who maintained a look of intense interest as they were escorted to the library entrance. The soldiers milled around in some confusion. Wu approached the black wall, hands held up, and touched the smooth surface with his fingers and palms.

It did not dilate, as he had been told to expect. He stepped back and lowered his hands. "Sorry," he said. "It doesn't seem—"

A low, vibrating series of tones issued from the wall, and repeated, followed by a voice. "Police attention required in this precinct," the voice said in Russian. "No entrance to unauthorized personnel. Please alert medical and police authorities immediately. No entrance allowed." It then repeated its message in English and Chinese.

The soldiers backed away, AKVs unslung and pistols drawn.