He could hear the relief in her voice. He put the receiver back. "Is it that bad?"

"We just got the preliminary ident back. It's definitely a Type A myxovirus. Influenza."

He had been expecting something worse, some third world fever or a retrovirus. He had had the flu back in the days before antivirals. He had felt terrible, congested, feverish, achy, for a few days and then gotten over it without anything but bedrest and fluids.

"Will they call the quarantine off then?"

"Not until we get Badri's medical records," she said. "I keep hoping he skipped his last course of antivirals. If not, then we'll have to wait till we locate the source."

"But it's only the flu."

"If there's a small antigenic shift, a point or two, it's only the flu," she corrected him. "If there's a large shift, it's influenza, which is an entirely different matter. The Spanish Flu pandemic of 1918 was a myxovirus. It killed twenty million people. Viruses mutate every few months. The antigens on their surface change so that they're unrecognizable to the immune system. That's why seasonals are necessary. But they can't protect against a large point shift."

"And that's what this is?"

"I doubt it. Major mutations only happen every ten years or so. I think it's more likely that Badri failed to get his seasonals. Do you know if he was running an on-site at the beginning of term?"

"No. He may have been."

"If he was, he may simply have forgotten to go in for them, in which case all he has is this winter's flu."

"What about Kivrin? Has she had her seasonals?"

"Yes, and full-spectrum antivirals and T-cell enhancement. She's fully protected."

"Even if it's influenza?"

She hesitated a fraction of a second. "If she was exposed to the virus through Badri this morning, she's fully protected."

"And if she saw him before then?"

"If I tell you this, you'll only worry, and I'm certain there's no need to." She took a breath. "The enhancement and the antivirals were given so that she would have peak immunity at the beginning of the drop."

"And Gilchrist moved the drop up by two days," Dunworthy said bitterly.

"I wouldn't have allowed her to go through if I hadn't thought it was all right."

"But you hadn't counted on her being exposed to an influenza virus before she even left."

"No, but it doesn't change anything. She has partial immunity, and we're not certain she was even exposed. Badri scarcely went near her."

"And what if she was exposed earlier?"

"I knew I shouldn't have told you," Mary said. She sighed. "Most myxoviruses have an incubation period of from twelve to forty-eight hours. Even if Kivrin was exposed two days ago, she'd have had enough immunity to prevent the virus from replicating sufficiently to cause anything but minor symptoms. But it's not influenza." She patted his arm. "And you're forgetting the paradoxes. If she'd been exposed, she'd have been highly contagious. The net would never have let her through."

She was right. Diseases couldn't go through the net if there was any possibility of the contemps contracting them. The paradoxes wouldn't allow it. The net wouldn't have opened.

"What are the chances of the population in 1320 being immune?" he asked.

"To a modern-day virus? Almost none. There are eighteen hundred possible mutation points. The contemps would have all had to have had the exact virus, or they'd be vulnerable."

Vulnerable. "I want to see Badri," he said. "When he came to the pub, he said there was something wrong. He kept repeating it in the ambulance on the way to the hospital."

"Something is wrong," Mary said. "He's got a serious viral infection."

"Or he knows he exposed Kivrin. Or he didn't get the fix."

"He said he got the fix." She looked sympathetically at him. "I suppose it's useless to tell you not to worry about Kivrin. You saw how I've just acted over Colin. But I meant it when I said they're both safer out of this. Kivrin's much better off where she is than she would be here, even among those cutthroats and thieves you persist in imagining. At least she won't have to deal with NHS quarantine regulations

He smiled. "Or American change ringers. America hadn't been discovered yet." He reached for the door handle.

The door at the end of the corridor banged open and a large woman carrying a valise barged through it. "There you are, Mr. Dunworthy," she shouted the length of the corridor. "I've been looking everywhere for you."

"Is that one of your bell ringers?" Mary said, turning to look down the corridor at her.

"Worse," Dunworthy said. "It's Mrs. Gaddson."

It was growing dark under the trees and at the bottom of the hill. Kivrin's head began to ache before she had even reached the frozen wagon ruts, as if it had something to do with microscopic changes in altitude or light.

She couldn't see the wagon at all, even standing directly in front of the little chest, and squinting into the darkness past the thicket made her head feel even worse. If this was one of the "minor symptoms" of time-lag, she wondered what a major one would be like.

When I get back, she thought, struggling through the thicket, I intend to have a little talk with Dr. Ahrens on the subject. I think they are underestimating the debilitating effects these minor symptoms can have on an historian. Walking down the hill had left her more out of breath than climbing it had, and she was so cold.

Her cloak and then her hair caught on the willows as she pushed her way through the thicket, and she got a long scratch on her arm that immediately began to ache, too. She tripped once and nearly fell flat, and the effect on her headache was to jolt it so that it stopped hurting and then returned with redoubled force.

It was almost completely dark in the clearing, though what little she could see was still very clear, the colors not so much fading as deepening toward black — black-green and black-brown and black-gray. The birds were settling in for the night. They must have got used to her. They didn't so much as pause in their pre- bedtime twitterings and settlings down.

Kivrin hastily grabbed up the scattered boxes and splintered kegs, and flung them into the tilting wagon. She took hold of the wagon's tongue and began to pull it toward the road. The wagon scraped a few inches, slid easily across a patch of leaves, and stuck. Kivrin braced her foot and pulled again. It scraped a few more inches and tilted even more. One of the boxes fell out.

Kivrin put it back in and walked around the wagon, trying to see where it was stuck. The right wheel was jammed against a tree root, but it could be pushed up and over, if only she could get a decent purchase. She couldn't on this side — Mediaeval had taken an ax to this side so that it would look like the wagon had been smashed when it overturned, and they had done a good job. It was nothing but splinters. I told Mr. Gilchrist he should have let me have gloves, she thought.

She came around to the other side, took hold of the wheel, and shoved. It didn't budge. She pulled her skirts and cloak out of the way and knelt beside the wheel so she could put her shoulder to it.

The footprint was in front of the wheel, in a little space swept bare of leaves and only as wide as the foot. The leaves had drifted up against the roots of the oaks on either side. The leaves did not hold a print that she could see in the graying light, but the print in the dirt was perfectly clear.

It can't be a footprint, Kivrin thought. The ground is frozen. She reached out to put her hand in the indentation, thinking it might be some trick of shadow or the failing light. The frozen ruts out in the road would not have taken any print at all. But the dirt gave easily under her hand, and the print was deep enough to feel.