Dunworthy hadn't heard that argument since the early years of the nets, when the theory was only partially understood.

"I assure you we've taken every precaution," Gilchrist said.

"Nothing that would affect the course of history can go through a net," Dunworthy explained, glaring at Gilchrist. The man was simply encouraging her with this talk of precautions and probabilities. "Radiation, toxins, microbes, none of them has ever passed through a net. If they're present the net simply won't open."

The medic looked unconvinced.

"I assure you — " Gilchrist said, and Mary came in.

She was carrying a sheaf of variously-colored papers. Gilchrist stood up immediately. "Dr. Ahrens, is there a possibility that this viral infection Mr. Chaudhuri has contracted might have come through the net?"

"Of course not," she said, frowning as if the whole idea were ridiculous. "In the first place, diseases can't come through the net. It would violate the paradoxes. In the second place, if it had, which it can't, Badri would have caught it less than an hour after it came through, which would mean the virus had an incubation period of an hour, an utter impossibility. But if it did, which it can't, you all would be down ill already," she looked at her digital, "since it's been over three hours since you were exposed to it." She began collecting the contacts lists.

Gilchrist looked irritated. "As Acting Head of the History Faculty I have responsibilities I must attend to," he said. "How long do you intend to keep us here?"

"Only long enough to collect your contacts lists," she said. "And to give you your instructions. Perhaps five minutes."

She took Latimer's list from him. Montoya grabbed hers up from the end table and began writing hastily.

"Five minutes?" the medic who had asked about the virus coming through the net said. "Do you mean we're free to go?"

"On medical probation," she said. She put the lists at the bottom of her sheaf of papers and began passing the top sheets, which were a virulent pink, around to everyone. They appeared to be a release form of some sort, absolving the infirmary of any and all responsibility.

"We've completed your blood tests," she went on, "and none of them show an increased level of antibodies."

She handed Dunworthy a blue sheet which absolved the NHS of any and all responsibility and confirmed willingness to pay any and all charges not covered by the NHS in full and within thirty days.

"I've been in touch with the WIC, and their recommendation is controlled observation, with continuous febrile monitoring and blood samples at twelve-hour intervals."

The sheet she was distributing now was green and headed, "Instructions for Primary Contacts." Number one was, "Avoid contact with others."

Dunworthy thought of Finch and the bellringers waiting, no doubt, at the gate of Balliol with summons and Scriptures, and of all those Christmas shoppers and detainees between here and there.

"Record your temp at one-half hour intervals," she said, passing round a yellow form. "Come in immediately if your monitor," she tapped at her own, "shows a marked increase in temp. Some fluctuation is normal. Temps tend to rise in the late afternoon and evening. Any temp between 36 and 37.4 is normal. Come in immediately if your temp exceeds 37.4 or rises suddenly, or if you begin to feel any symptoms — headache, tightness in the chest, mental confusion, or dizziness."

Everyone looked at his or her monitor, and, no doubt, began to feel a headache coming on. Dunworthy had had a headache all afternoon.

"Avoid contact with others as much as possible," Mary said. "Keep careful track of any contacts you do have. We're still uncertain of the mode of transmission, but most myxoviruses spread by droplet and direct contact. Wash your hands with soap and water frequently."

She handed Dunworthy another pink sheet. She was running out of colours. This one was a log, headed "Contacts," and under it, "Name, Address, Type of contact, Time."

It was unfortunate that Badri's virus had not had to deal with the CDC, the NHS and the WIC. It would never have got in the door.

"You must report back here at seven tomorrow morning. In the meantime, I'd recommend a good supper and then to bed. Rest is the best defense against any virus. You are off-duty," she said, looking at the medics, "for the duration of the temp quarantine." She passed out several more rainbow-hued papers and then asked brightly, "Any questions?"

Dunworthy looked at the medic, waiting for her to ask Mary if smallpox had come through the net, but she was looking uninterestedly at her clutch of papers.

"Can I go back to my dig?" Montoya asked.

"Not unless it's inside the quarantine perimeter," Mary said.

"Well, great," she said, jamming her papers angrily into the pockets of her terrorist jacket. "The whole village will have washed away while I'm stuck here." She stomped out.

"Are there any other questions?" Mary said imperturbably. "Very well, then, I'll see you all at seven o'clock."

The medics ambled out, the one who had asked about the virus yawning and stretching as if she were preparing for another nap. Latimer was still sitting down, watching his temp monitor. Gilchrist said something snappish to him, and he got up and put his coat on and collected his umbrella and his stack of papers.

"I expect to be kept informed of every development," Gilchrist said. "I am contacting Basingame and telling him it's essential that he return and take charge of this matter." He swept out and then had to wait, holding the door open, for Latimer to pick up two papers he had dropped.

"Go round in the morning and collect Latimer, won't you?" Mary said, looking through the contacts lists. "He'll never remember he's to be here at seven."

"I want to see Badri," Dunworthy said.

"'Laboratory, Brasenose,'" she said, reading from the sheets. "'Dean's office, Brasenose. Laboratory, Brasenose.' Didn't anyone see Badri except in the net?"

"In the ambulance on the way here he said, 'Something wrong.' There could have been slippage. If she's more than a week off, she'll have no idea when to rendezvous."

She didn't answer. She sorted through the sheets again, frowning.

"I need to make certain there weren't any problems with the fix," he said insistently.

She looked up. "Very well," she said. "These contact sheets are hopeless. There are great gaps in Badri's whereabouts for the past three days. He's the only person who can tell us where he was and with whom he came in contact." She led the way back down the corridor. "I've had a nurse with him, asking him questions, but he's very disoriented and fearful of her. Perhaps he won't be as frightened of you."

She led the way down the corridor to the lift and said, "Ground floor, please," into its ear. "Badri's only conscious for a few moments at a time," she said to Dunworthy. "It may be most of the night."

"That's all right," Dunworthy said. "I won't be able to rest till I'm sure Kivrin is safely through."

They went up two flights in the lift, down another corridor, and through a door marked, "NO ENTRANCE. ISOLATION WARD." Inside the door, a grim-looking ward sister was sitting at a desk watching a monitor.

"I'm taking Mr. Dunworthy in to see Mr. Chaudhuri," Mary said. "We'll need SPG's. How is he?"

"His fever's up again. 39.5," the sister said, handing them the SPG's, which were plastene-sealed bundles of paper clothing gowns that stripped up the back, caps, imperm masks that were impossible to get on over the caps, bootie-like snugs that went on over their shoes, and imperm gloves. Dunworthy made the mistake of putting his gloves on first and took what seemed like hours attempting to unfold the gown and affix the mask.

"You'll need to ask very specific questions," Mary said. "Ask him what he did when he got up this morning, if he'd stayed the night with anyone, where he ate breakfast, who was there, that sort of thing. His high fever means that he's very disoriented. You may have to ask your questions several times." She opened the door to the room.