Wolgast slept, now, on the first floor of the lodge, in a chair facing the door. They move at night, Carl had told him, in the trees. You get one shot. What were they, these things in the trees? Were they people, as Carter had once been a person? What had they become? And Amy. Amy, who dreamed of voices, whose hair did not grow, who seemed rarely to sleep—for it was true, he’d realized she was only pretending—or to eat; who could read and swim as if she were remembering lives and experiences other than her own: was she part of them, too? The virus was inert, Fortes had said. What if it wasn’t? Wouldn’t he, Wolgast, be sick? But he wasn’t; he felt just as he’d always felt, which was, he realized, simply bewildered, like a man in a dream, lost in a landscape of meaningless signs; the world had some use for him he didn’t understand.

Then on a night in March he heard an engine. The snow was heavy and deep. The moon was full. He had fallen asleep in the chair. He realized he’d been hearing, as he’d slept, the sound of an engine coming down the long drive toward the lodge. In his dream—a nightmare—this sound had become the roar of the fires of summer, burning up the mountain toward them; he had been running with Amy through the woods, the smoke and fire all around, and lost her.

A blaze of light in the windows, and footsteps on the porch—heavy, stumbling. Wolgast rose quickly, all his senses instantly alert. The Springfield was in his hand. He racked the slide and released the safety. The door shook with three hard pounds.

“Somebody’s outside.” The voice was Amy’s. Wolgast turned and saw her standing at the bottom of the stairs.

“Upstairs!” Wolgast spoke to her in a harsh whisper. “Go, quickly!”

“Is anybody inside there?” A man’s voice on the porch. “I can see the smoke! I’ll step away!”

“Amy, upstairs, now!”

More pounding on the door. “For godsakes, somebody, if you can hear me, open the door!”

Amy retreated up the stairs. Wolgast moved to the window and looked out. Not a car or truck but a snowmobile, with containers lashed to its chassis. In the headlights, at the foot of the porch, was a man in a parka and boots. He was positioned in a crouch, his hands on his knees.

Wolgast opened the door. “Keep back,” he warned. “Let me see your hands.”

The man lifted his arms weakly. “I’m not armed,” he said. He was panting, and that was when Wolgast saw the blood, a bright ribbon down the side of his parka. The wound was in his neck.

“I’m sick,” the man said.

Wolgast stepped forward and raised his gun. “Get out of here!”