The safest route would be along the edge of the bridge, where they could hold onto the guardrail as they stepped from beam to beam. The feel of the cold metal on his hands was like fire, an exquisite sharpness. They couldn’t get this done fast enough. Amy went first, skipping with confident grace over the gaps. As he made to follow her, it became instantly clear that the problem wasn’t the beams themselves, which seemed solid, but what encased them, under the snow: a hidden skin of ice. Twice Peter felt himself losing traction, his feet slipping out from under him, his hand biting into the frigid rail, barely holding on. But to come this far, only to drown in an icy river—he couldn’t imagine it. Slowly, beam by beam, he made his way across. By the time he reached the far side, Peter’s hands felt utterly numb; he had begun to shiver. He wished they could stop to build a fire, but there was no delaying their progress now. Already the shadows had begun to lengthen; the brief winter day would soon be over.

They ascended the bank of the river and began to climb. Wherever they were going, he hoped there would be shelter. He didn’t see how they would last the night without it. Never mind the virals; cold like this could kill them just as easily. The important thing was to keep moving. Amy had taken the lead, her strides carrying her up the mountain. It was all Peter could do to keep up. The air felt thin in his lungs; around him the trees were moaning in the wind. After a period of time had passed he looked back and beheld the valley far below them, the river curling through it. They were in shadow now, a zone of twilight, but on the far side of the valley, the faces of the mountains, receding to the north and east, thrummed with golden light. The top of the world, Peter thought, that’s where Amy is taking me. The very top of the world.

The day drained away. In the descending gloom, the landscape appeared as a confusing jumble; what Peter had thought would be the apex of their climb revealed itself to be a crest in a series of ascents, each more exposed and wind-blasted than the last. To the west the mountain fell away sharply, an almost sheer drop. The cold seemed to have reached some deeper place inside him, dulling his senses. It had been a mistake, he realized, to send the horse away. If push came to shove, they could at least have hiked back down and used his body for warmth and shelter. It was a grave thing, to kill such an animal, nothing he could have imagined doing before; but now, as darkness was falling on the mountain, he knew he could have done it.