"Oxygen?" the nurse said.

"Not yet," the house officer said on his way out. "Start him on 200 units of chloramphe nicol."

The nurse laid Badri back down, attached a piggyback to the drip, watched Badri's temp drop for a minute, and went out.

Dunworthy looked out the window at the rainy night. "I remember feeling odd," he had said. Not ill. Odd. Someone who'd never had a cold wouldn't know what to make of a fever or chills. He would only have known something was wrong and would have left the net and hurried to the pub to tell someone. Have to tell Dunworthy. Something wrong.

Dunworthy took off his spectacles and rubbed his eyes. The disinfectant made them smart. He felt exhausted. He had said he couldn't relax until he knew Kivrin was all right. Badri was asleep, the harshness of his breathing taken away by the impersonal magic of the doctors. And Kivrin was asleep, too, in a flea-ridden bed seven hundred years away. Or wide-awake, impressing the contemps with her table manners and her dirty fingernails, or kneeling on a filthy stone floor, telling her adventures into her hands.

He must have dozed off. He dreamed he heard a telephone ringing. It was Finch. He told him the Americans were threatening to sue for insufficient supplies of lavatory paper and that the Dean had called with the Scripture. "It's Matthew 2:11," Finch said. "Waste leads to want," and at that point the nurse opened the door and told him Mary needed him to meet her in Casualties.

He looked at his digital. It was twenty past four. Badri was still asleep, looking almost peaceful. The nurse met him outside with the disinfectant bottle and told him to take the elevator.

The smell of disinfectant from his spectacles helped wake him up. By the time he reached the ground floor he was almost awake. Mary was there waiting for him in a mask and the rest of it. "We've got another case," she said, handing him a bundle of SPG's. "It's one of the detainees. It might be someone from that crowd of shoppers. I want you to try to identify her."

He got into the garments as clumsily as the first time, nearly tearing the gown in his efforts to get the velcro strips apart. "There were dozens of shoppers on the High," he said, pulling the gloves on. "And I was watching Badri. I doubt that I could identify anyone on that street."

"I know," Mary said. She led the way down the corridor and through the door to casualties. It seemed like years since he'd been there.

Ahead, a cluster of people, all anonymous in paper, were wheeling a stretcher trolley in. The house officer, also papered, was taking information from a thin, frightened-looking woman in a wet mackintosh and matching rain hat.

"Her name is Beverly Breen," she told him in a faint voice. "226 Plover Way, Surbiton. I knew something was wrong. She kept saying we needed to take the tube to Northampton."

She was carrying an umbrella and a large handbag, and when the house officer asked for the patient's NHS number, she leaned the umbrella against the admissions desk, opened the handbag, and looked through it.

"She was just brought in from the tube station complaining of headache and chills," Mary said. "She was in line to be assigned lodging."

She signaled the medics to stop the stretcher trolley and pulled the blanket back from the woman's neck and chest so he could get a better look at her, but he didn't need it.

The woman in the wet mac had found the card. She handed it to the officer, picked up the umbrella, the handbag and a sheaf of varicoloured papers and came over to the stretcher trolley carrying them. The umbrella was a large one. It was covered with lavender violets.

"Badri collided with her on the way back to the net," he said.

"Are you absolutely certain?" Mary said.

He pointed at the woman's friend, who had sat down now and was filling out forms. "I recognize the umbrella."

"What time was that?" she said.

"I'm not positive. Half-past one?"

"What type of contact was it? Did he touch her?"

"He ran straight into her," he said, trying to recall the scene. "He collided with the umbrella, and then he told her he was sorry, and she yelled at him for a bit. He picked up the umbrella and handed it to her."

"Did he cough or sneeze?"

"I can't remember."

The woman was being wheeled into Casualties. Mary stood up. "I want her put in isolation," she said, and started after them.

The woman's friend stood up, dropping one of the forms and clutching the others awkwardly to her chest. "Isolation?" she said frightenedly. "What's wrong with her?"

"Come with me, please," Mary said to her and led her off somewhere to have her blood taken and her friend's umbrella spritzed with disinfectant before Dunworthy could ask her whether she wanted him to wait for her. He started to ask the registrar and then sat down tiredly in one of the chairs against the wall. There was an inspirational brochure on the chair next to him. Its title was "The Importance of a Good Night's Sleep."

His neck hurt from his uncomfortable sleep on the campstool, and his eyes were smarting again. He supposed he should go back up to Badri's room, but he wasn't certain he had the energy to put on another set of SPG's. And he didn't think he could bear to wake Badri and ask him who else would be shortly wheeled into casualties with a temp of 39.5.

At any rate Kivrin wouldn't be one of them. It was half past four. Badri had collided with the woman with the lavendar umbrella at half past one. That meant an incubation of fifteen hours, and fifteen hours ago Kivrin had been fully protected.

Mary came back, her cap off and her mask dangling from her neck. Her hair was in disarray, and she looked as bone-weary as Dunworthy felt.

"I'm discharging Mrs. Gaddson," she told the registrar. "She's to be back here at seven for a blood test." She came over to where Dunworthy was sitting. "I'd forgotten all about her," she said, smiling. "She was rather upset. She threatened to sue me for unlawful detainment."

"She should get along well with my bell ringers. They're threatening to go to court over involuntary breach of contract."

Mary ran her hand through her disorderly hair. "We got an ident from the World Influenza Center on the influenza virus." She stood up as if she had had a sudden infusion of energy. "I could do with a cup of tea," she said. "Come along."

Dunworthy glanced at the registrar, who was watching them attentively, and hauled himself to his feet.

"I'll be in the surgical waiting room," Mary said to the registrar.

"Yes, Doctor," the registrar said. "I couldn't help overhearing your conversation…" she said hesitantly.

Mary stiffened.

"You told me you were discharging Mrs. Gaddson, and then I heard you mention the name 'William,' and I was just wondering if Mrs. Gaddson is by any chance William Gaddson's mother."

"Yes," Mary said, looking puzzled.

"You're a friend of his?" Dunworthy said, wondering if she would blush like the blonde student nurse.

She did. "I've come to know him rather well this vac. He's stayed up to read Petrarch."

"Among other things," Dunworthy said, and while she was busy blushing, steered Mary past the "NO ENTRANCE: ISOLATION AREA" sign and down the corridor.

"What in heaven's name was that all about?" she asked.

"Sickly William is even more self-sufficient than we had at first assumed," he said, and opened the door to the waiting room.

Mary flicked the light on and went over to the tea trolley. She shook the electric kettle and disappeared into the WC with it. He sat down. Someone had taken away the tray of blood- testing equipment and moved the end table back to its proper place, but Mary's shopping bag was still sitting in the middle of the floor. He leaned forward and moved it over next to the chairs.