Slater had to agree. Digging up graves under any circumstances was a harrowing business, rife with potential problems. But digging up graves containing the hundred-year-old remains of victims of the Spanish flu — remains that might have deteriorated, in coffins that might have disintegrated, in graves that might even have shifted their location underground due to geothermal changes — was a task requiring the utmost care and professional expertise.

Not to mention sensitivity. It was no surprise to Slater that he saw Nika lacing up her boots and slipping on her glove liners.

“I don’t suppose I could persuade you to stay out of harm’s way today?” Slater said.

“Thanks, but after last night,” she said, “I think I’ve already had my baptism by fire.”

Sergeant Groves, with a bundle of wire flags under his arm, smiled and shook his head at his boss, as if to say, You were dreaming if you thought she wasn’t coming. And though Slater knew he was right, he had had to give it a try. In addition to all the other considerations, exhumations were often dangerous affairs, and the first thing any team leader tried to do was limit the personnel present.

The second thing was to avoid wasting time on battles with headstrong opponents who were bound and determined to pursue their own agenda no matter what.

The sky was a sullen gray when the team finally passed under the main gates of the colony and started down the cleared slope that led to the grove of trees. Slater spotted a narrow break in the woods that suggested a trail had once begun here, and without a word Sergeant Groves wired a red flag to the nearest bough. As they forced their way through the thick trees and dense underbrush, brambles pulling at the sleeves of their coats and low-hanging branches dropping their load of fresh snow on top of their hoods and hats, Groves continued to place an occasional marker along the way.

“We’ll need all of this cut away on both sides,” Slater said, over his shoulder, and Groves replied, “I can get a team with power saws down here later this afternoon. You want ramping, too?”

“Yes, wherever the ground is particularly uneven.”

“Yes, please, I will need that,” the professor said, as he struggled with Nika’s help to steer the wheels of his GPR around an especially gnarly root formation.

Slater, seeing the difficulty he was having, resisted saying I told you so. He understood the professor’s impatience to get started; it was a failing, or virtue, in his own nature, too. But years of running epidemiological missions had taught him to rein in his impulses by making a careful plan and following it to the letter.

“What do you want to do about lighting?” Groves asked.

“A halogen stanchion every twenty feet or so, maybe three hundred watts each.”

“I was afraid you’d say that.”

Slater knew that it would mean running a lot of cables and power from the generators in the colony all the way through the forest, but they were going to have to do that, anyway, to power up the dressing and decontamination chamber.

When they did emerge from the trees again, Slater stopped at a pair of weathered gateposts, with something — some word or two — whittled into the wood.

Nika immediately removed a glove and reverently ran one finger over the faint writing. “It’s Russian.”

And when Kozak stepped forward and leaned close enough to see, he said, “It’s the same thing, over and over again.”

“What?” Groves asked.

“It says, ‘Forgive me, forgive me.’ ”

“I wonder why,” Nika said, softly.

But Slater, surveying the graveyard that extended all the way to the cliffside, wondered who had scrawled it there. Had it been the founder of the sect, who had brought his flock to ruin in such a bleak and unforgiving spot? Had it been the last surviving member of the colony?

Or could it have been the carrier himself, aware of the calamity he had brought upon his fellows?

The chances of their ever finding out were slim, nor could he allow himself to become distracted by such questions. Right now, looking out across the desolate cemetery, with its tilting crosses and broken tombstones, he was assessing the lay of the land. Glancing to his left, he saw a cleared spot covered only by a soft white duvet of snow.

“We’ll build the biohazard prefab there,” he told Groves, who was already sticking more of his wire flags into the ground to demarcate its boundaries. He’d erected such structures before and knew that he needed a space about eight feet square. These chambers were always a tight squeeze, but the bigger they got, the more chances there were for a sprung seam or a loose flap compromising the whole thing.

Kozak was already trundling his GPR, on its four hard rubber wheels, between the gateposts and onto the grounds of the graveyard. Parking it beside a rotted tree stump, he pounded his boots on the soil, almost as if he were starting some dance, then knelt, pulling off his gloves, and rubbed the snow and frost away from a patch of earth. He sifted a few grains between his thick fingers, then pressed his cheek against the ground as if he were listening for a heartbeat. Slater and Nika exchanged an amused look, but Slater knew that there had to be a good reason for everything he was doing. Kozak was the best at what he did and he could read the earth like nobody else. Slapping the ground several times, then brushing the dirt from his palms and pants, he declared, “The first foot or two is permafrost, but we can cut through. Three or four feet down, there is bedrock.”

For Slater, that was good news. The graves would have had to be shallow ones.

“But I will need to do a thorough GPR survey of the whole area.”

“There won’t be time,” Slater said, thinking of his timetable, and of the winter storms bearing down from Siberia any day now. “Start over by the precipice, where the erosion’s already started. I need to know that the ground we’ll be working on tomorrow is stable.”

At the edge of the graveyard, there was a gouge in the earth, where the overhanging rock and soil had dropped off into the Bering Sea like a broken diving board. As Slater approached the spot, he felt Kozak grab his sleeve and say, “Wait.”

Pushing the GPR like a stroller, Kozak moved slowly past him, all the while intently studying the computer monitor that was mounted between the two red handles. Nika, at his elbow, looked entranced by the shadowy black-and-white imagery appearing on the screen, and Kozak was only too happy to explain what the images, and the accompanying numbers scrolling down both sides of the monitor, conveyed.

“The transducer,” he said, pointing to one of the twin black antennae mounted on the lower part of the carriage, “is sending pulses of energy into the ground. These pulses, they penetrate materials with different electrical conduction properties and make a kind of reflection, here,” he said, tapping the interface screen. “It is something called dielectric permittivity. And the data, it is all stored in the computer.”

“What’s the data telling you right now?” Slater asked as they approached the graves closest to the edge of the precipice.

Kozak paused before answering. “I will need to analyze it later. But there is something strange. Either the monitor is malfunctioning, or the ground has fracture lines that are not geological in origin.”

“Oh, you mean from when the graves were dug?” the sergeant surmised.

“Something more than that,” Kozak said, still looking a bit puzzled. He pushed the GPR carriage over the plot closest to the area were the cliff had given way, then moved it back and forth slowly, from the top of the grave to its foot. Slater craned his neck to look at the monitor himself, and it vaguely reminded him of looking at a sonogram. What he saw there was a fuzzy image of a long rectangle, with something sharper and harder depicted in the middle of the space. But when Kozak rolled the GPR back again one more time, Slater could see that the edges of the image grew wider and more irregular. Blurred. He could guess what that meant, but he waited for Kozak to say it.