“Be careful.”

D’Agosta shouldered his small knapsack and retreated to the back side of the hill, making his way down through bare trees, scrub, and mountain laurel. Everything was sopping wet, and water dripped from the trees. Here and there, small patches of damp snow glistened beneath the branches. He didn’t need a light once he’d rounded the hill-there was enough glow from Herkmoor to light up most of the mountain.

D’Agosta was glad of the activity. During the wait on top, he’d had too much time to think. And thinking was the last thing he wanted to do: thinking about his upcoming disciplinary trial, which might very well end in his dismissal from the NYPD. It seemed incredible what had happened in the last few months: his sudden promotion to the NYPD; his blossoming relationship with Laura Hayward; his reconnection with Agent Pendergast. And then it had all come crashing down. His career as a cop was in deep shit; he was estranged from Hayward; and his friend Pendergast was rotting in that damp hell below, shortly to go on trial for his life.

D’Agosta staggered, righted himself. He tilted his bleary face upward, letting the drops of icy rain lash a modicum of alertness into him.

He wiped his face and pushed on. Getting the water sample was going to be tricky, since the stream flowed along the edge of an open field outside the prison walls, completely exposed to the guards in the towers. But this was nothing compared to the magnetic drag he was charged with performing. Glinn wanted him to crawl as close to the outer perimeter fence as he could get, carrying a miniature magnetometer in his pocket, to see if there were any buried sensors or hidden electromagnetic fields… and then plant the damn thing in the ground. Of course, if there were any sensors, he might well set them off-and then things would get exciting.

He crept slowly downhill, the ground gradually leveling out. Despite his slicker and gloves, he could feel the icy water creeping down his legs and in through the poor sealing of his boots. A hundred yards farther on, he could make out the edge of the woods and hear the gurgle of the stream. He kept low in the laurel bushes as he moved forward. The last few yards he got down on his hands and knees and crawled.

A moment later, he was at the edge of the brook. It was dark and smelled of damp leaves, and along one bank a scalloped edge of old, rotten ice stubbornly remained.

He paused, looking at the prison. The guard towers loomed above now, only two hundred yards distant, the bright lights like multiple suns. He fumbled in his pocket and was about to remove the vial Glinn had given him when he froze. His assumption that the guards would be looking inward, toward the prison, had been wrong: he could clearly see one of them looking out, scanning the edge of the woods nearby with high-powered binoculars.

An important detail.

He froze, flattening himself in the laurel. He had already entered the forbidden perimeter, and he felt horribly exposed to view.

The guard’s attention seemed to have swept past him. With exaggerated care, he edged forward and dipped the vial into the icy water, filled it, then screwed the top back on. Then he crept downstream, fishing out trash-old Styrofoam coffee cups, a few beer cans, gum wrappers-and putting it in the knapsack. Glinn had been quite insistent that D’Agosta collect everything. It was a highly unpleasant job, wading in the icy water, sometimes having to root about the cobbled stream bottom up to his shoulder in water. One jam-up of branches across the stream acted like a sieve and he hit the jackpot, collecting a good ten pounds of sodden garbage.

When he was done, he found himself at the point downstream where Glinn wanted the magnetometer placed. He waited until the guard’s attention was at the farthest point; then he half waded, half crawled across the stream. The meadow that surrounded the prison was unkempt, grasses dead and flattened by the winter snows. But there were just enough skeletal weeds to provide at least the semblance of cover.

D’Agosta crawled forward, freezing in place every time the guard swept the binoculars his way.

The minutes crawled by. He felt the icy drizzle trickling down his neck and back. The fence grew closer only by excruciating degrees of slowness. But he had to keep going, and as fast as he dared: the longer he lingered, the higher the probability that one of the guards would spot him.

At last he reached the groomed part of the lawn. He removed the device from his pocket, pushed one hand out through the tall weeds, sank the magnetometer down to the level of the grass, then began an awkward retreat.

Crawling back was much more difficult. Now he was facing the wrong direction and unable to monitor the guard towers. He kept on, slowly but steadily, with frequent long pauses. Forty-five minutes after setting out, he once again crossed the stream and reentered the dripping woods, pushing up through the laurel bushes toward their spy nest on top of the hill, feeling half frozen, his back aching from lugging the knapsack of wet trash.

“Mission accomplished?” Proctor asked as he returned.

“Yeah, assuming I don’t lose my frigging toes to frostbite.”

Proctor adjusted a small unit. “Signal’s coming in nicely. It appears you got within fifty feet of the fence. Nice work, Lieutenant.”

D’Agosta turned wearily toward him. “Call me Vinnie,” he said.

“Yes, sir.”

“I’d call you by your first name, but I don’t know what it is.”

“Proctor is fine.”

D’Agosta nodded. Pendergast had surrounded himself with people almost as enigmatic as himself. Proctor, Wren… and in the case of Constance Greene, maybe even more enigmatic. He checked his watch again: almost two.

Fourteen hours to go.

Rain hammered against the crumbling brick-and-marble facade of the Beaux Arts mansion at 891 Riverside Drive. Far above the mansard roof and its widow’s walk, lightning tore at the night sky. The first-floor windows had been boarded up and covered with tin, and the windows of the upper three stories were securely shuttered-no light pierced through to betray life within. The fenced front yard was overgrown with sumac and ailanthus bushes, and stray bits of wind-whipped trash lay in the carriage drive and beneath the porte cochere. In every way, the mansion appeared abandoned and deserted, like many others along that bleak stretch of Riverside Drive.

For a great many years-a truly remarkable number of years, in fact-this house had been the shelter, redoubt, laboratory, library, museum, and repository for a certain Dr. Enoch Leng. But after Leng’s death, the house had passed through obscure and secret channels-along with the charge of Leng’s ward, Constance Greene-to his descendant, Special Agent Aloysius Pendergast.

But now, Agent Pendergast was in solitary confinement in the maximum security wing of Herkmoor Correctional Facility, awaiting trial for murder. Proctor and Lieutenant D’Agosta were away on a reconnaissance of the prison. The queer excitable man known as Wren, who was Constance Greene’s nominal guardian while Pendergast was gone, was at his night job at the New York Public Library.

Constance Greene was alone.

She sat before a dying fire in the library, where neither the sounds of rain nor those of traffic penetrated. She had before her My Life by Giacomo Casavecchio, and she was intently studying the Renaissance spy’s account of his celebrated escape from the Leads, the dreaded prison in the Venetian Ducal Palace from which no one had ever escaped before-or would escape again. A stack of similar volumes covered a nearby table: accounts of prison escapes from all over the world, but especially focusing on the federal correctional system in the United States. She read in silence, every so often pausing to make a notation in a leather-bound notebook.