Because of the erratic schedules of scientists and researchers, the cafeteria was kept open around the clock, so he grabbed a quick sandwich and a Snapple. A couple of people said hi, and “Weren’t you overseas somewhere?” and he realized, with relief, that the news of his assault on a commanding officer and his subsequent court-martial hadn’t received much play here. The civilians on staff had no idea of its gravity — all they knew about military discipline was what they’d seen on episodes of JAG—and the army personnel were so involved in their own projects and plans, they weren’t concerned with anyone else’s.

He ate alone, and after tossing the sandwich wrapper and the empty bottle into the trash, he considered heading home, but then he thought, to what? An empty apartment? He could always go to the gym and work out, but there was something so forlorn about the gym at night. The fluorescent lights, the acrid odor of sweat that had been building up all day, the weary attendant mopping the locker-room floor. Not to mention all the other guys who, like him, had nowhere better to go.

And even if his body was flagging, his mind was still percolating just fine right now. That was both his blessing and his curse. It always had been. If his brain were equipped with an on/off switch, he had yet to find it. Nights were the worst. His thoughts could take him anywhere and everywhere; it was like a wild ride at an amusement park that never stopped. And right now the roller-coaster car was hurtling him along toward one destination in particular — the AFIP Tissue Repository, housed next door in the archives of the old Army Medical Museum. It had been founded, with his typical foresight and wisdom, by Abraham Lincoln himself — and it hadn’t changed all that much ever since.

The most comprehensive collection of tissue samples in the world, the Repository contained over 3 million specimens — among them pieces of lung tissue from a private at Camp Jackson, South Carolina, the first American soldier who had succumbed to the 1918 flu. Before setting out for the wilds of Alaska, Dr. Slater wanted to see the slides himself and get a look at this ancient enemy he was about to confront.

But when he tried his security card on the main concourse leading to the museum, he found there was a glitch in his clearance — no doubt another problem arising from his military discharge. And though he knew he could get it fixed the next day, that didn’t help him now. He passed the laminated card, which he wore on a chain around his neck, under the scanner one more time, just for luck, and watched as the lights stayed red. A third try he suspected would set off an internal alarm. He waited around in the corridor for a minute or two, hoping to piggyback on someone else going his way, but at this time of night the offices were largely deserted and no one else was around, much less heading over to the gloomy confines of the old museum.

Still, there was another route, and though it was a lot more circuitous, it would allow him to circumvent the particular security system obstructing him now. Going back toward his office, he took a sharp right through the environmental and toxicology wing, descended the fire stairs to the garage level, then walked briskly across the unheated, and nearly empty, garage. Not briskly enough, he thought, as he felt a sudden chill. He picked up the pace, scurrying down a flight of crumbling stairs that opened into a subbasement corridor, originally designed for the discreet unloading of cadavers by horse-drawn carriages in the years following the Civil War.

The hallways here were made of red brick, faded with age, and the lights in the ceiling, each one in a little wire nest, were incandescent bulbs, and low-wattage at that. The doors he passed bore frosted-glass panes, with gold hand lettering and labels that read HISTOLOGY, WAR WOUND RECORDS, or DEPARTMENT OF PALEOPATHOLOGY. It was hard to believe that this warren was still occupied, but Slater knew that the whole Walter Reed complex had long since outgrown its campus, and no nook or cranny was allowed to lie fallow for long.

As he turned the corner toward the Tissue Repository, he came upon the old display cases that had once been part of the public exhibitions. Although they were no longer part of any organized tours, the cabinets exhibited, on dusty shelves behind thick glass, a collection of formaldehyde-filled jars. Some of them dated back to the midnineteenth century, and held specimens of gross physical anomalies — twins conjoined at the torso, or fetuses born with the fused legs and feet of sirenomella victims. Because of their fishlike tails and amphibious eyes, they were named after the mythical sirens, or mermaids, and had seldom survived their birth by more than a day. Now, many decades later, they still floated, silently, intact, and unchanged, in the limbo of their murky jars.

Just inside the doors to the Repository, a night clerk in a crisply pressed tan uniform, his head down and earbuds in place, was typing away on his computer keyboard. He looked up in surprise when Slater entered, quickly yanked the buds, straightened in his chair, and slid a clipboard across the desk for Slater to sign in.

“I’ll need your ID, too,” he said. Slater held out his security card, while the clerk jotted down the number, then checked it online against the name on the register. Slater prayed that a problem wouldn’t crop up, but the clerk nodded, and said, “What can I do for you, sir?”

Slater explained what he was after, but as the clerk started to get up from his chair, he said, “You can stay put. I know my way around in here, and I can get it myself.”

“You sure?” the clerk said, sounding like he’d love to get back to what he’d been doing. Slater caught a glimpse on the computer of some video war game.

“Yes. It won’t take me long.”

And then, inexplicably, the clerk pulled some Kleenex from a box and handed a wad to Slater.

“What’s this for?”

“Pardon my saying so, sir, but you’re sweating.” He gestured at his forehead, and when Slater dabbed at his skin, the tissues did indeed come away damp.

“Thanks,” Slater said, “I guess I was in too big a hurry to get here.”

The clerk shrugged and, surveying the spooky vault, said, “That’ll be a first, sir.”

The Repository was huge, with several chambers interconnecting under brick archways, all of them retrofitted with rows of bright track lights mounted above microscope-equipped workstations. Long aisles were lined with endless rows of metal cabinets, each of them divided into drawers, no deeper than a deck of cards, containing the tissue and bone samples. Organized first by the pathology, then by the organic or anatomical origin, and then again by era, the samples had been gathered and sent to the archives from barracks and battlefields all over the world, and unless size was an issue, the oldest ones in any category were usually deposited in the bottom drawers of each section. It took Slater, who hadn’t been down in these archives for several years, a half hour just to find his way into the right corner of the right room. It was the last chamber in the chain, and like all the others he had passed through, no one else was in it.

Crouching down, he pulled out one drawer, checked the samples, closed it, and opened another. Here, he found what he was looking for. The last remains of Private Roscoe Vaughan, an artillery trainee at Camp Jackson, South Carolina, in 1918 … and the first known Army casualty of what had been dubbed, however inaccurately, the Spanish flu. Forty-three thousand others would follow him to the grave. Though it was little known, during the Great War, more of the doughboys had died from the flu than in combat.

All that was left of the private now was a block of paraffin, no bigger than a crouton, in which the Army surgeon, Captain K. P. Hedgeforth, had embedded slices of lung tissue he had taken from the dead soldier. Preserved in formaldehyde, the block had been dispatched to Washington and kept there in a little brown box on a shelf for nearly eighty years before its deadly secrets had been explored by AFIP scientists.