The marbles were some twenty or thirty yards ahead of her now, a hundred teetering balls, so very small inside the sealed arc of the sun. Their shadows seemed to burn themselves into the air. They were right on the verge of disappearing.

How far she must have come to make the sun so large.

How close she must have drawn to the horizon.

Most of the ice had already melted away, and soon she was leaping from one chunk to another, resting barely long enough to feel the pieces bob beneath her. Then the ice was gone altogether, and she was traveling directly across the surface of the water. Plants with long green fronds composed slow figure eights beneath her feet. Small fish darted past in the crimped light.

She had finally hit her stride. She imagined she could walk forever.

It soon became apparent to the blind man that the city was changing. The birds had returned to the air in greater numbers than ever before, and at times the vertical space around him seemed to warp or shift in some way so that he imagined he heard them all calling out from the exact same spot, a great mass of voices clustered together in a tree or on the railing of a balcony. Though the phenomenon never lasted for longer than a few seconds, it was quite distinct. The notes the birds gave out were sharp, multiangular – sudden little whistles that cut across one another like thorns.

He had heard this sound before. It was the saddest sound in the world: the sound of something that thought it was free but had come bumping up against the walls of its enclosure.

The birds might have been the first sign of the city's transformation (they were definitely the first that he noticed), but there were certainly others. The last of the snow ran to water, and it ceased to rain. The wind picked up speed one day, then reversed directions, and finally stopped blowing altogether. Once, the blind man accidentally kicked a pebble through a subway grate and never heard it hit the bottom.

He knew, then, that the topography of the city was changing, but he didn't know how, and he didn't know why, until the first few people came back from the edge of the monument district and the word began to spread. The rest of the city, that portion of it that lay beyond the park and the river, was no longer there. It had melted away along with the snow.

The blind man heard the story from a man who was holding court in the center of the shopping plaza. "I was thinking I would just go for a ride, you know, really open up and see what kind of speed I could do." His voice was coming from a crouch. He was spinning the pedals of his bicycle, then yanking them forward to make the chain seize short against the sprockets. "Well, I got as far as the six-laner at the other end of Park Street, and then I had to turn back around. The road wasn't there anymore. No sidewalks. No buildings. I'm not talking rubble or an empty field, you guys. I'm talking absolutely nothing."

"Why didn't you keep going?" someone asked him. "You know, see what was on the other side?"

"That's what I'm trying to tell you – there was no other side. I tried to keep pedaling, but it was like climbing up the inside of a sphere. I could feel myself moving, I just wasn't gaining any distance."

There was a sudden firecrackerlike string of side conversations. Then a few more people came together in the center of the plaza, and the structure of the crowd tightened, and the man with the bicycle began repeating his story. The blind man had already heard enough, though, and he left.

Later that day, there was a similar report from a man who had tried to leave the district by way of the suspension bridge, and there was another a few hours after that by a woman who had taken the same route the bicyclist had. The woman said that the highway was missing now, too, and that the city dead-ended at the gray strip of concrete where the hazard lane used to be. "This was all I found," she said, and she let something trickle through her fingers – a few cigarette butts and some fragments of window glass, from the sound of it. By that evening, half a dozen people must have made the journey to the border of the monument district and back. And so began the pilgrimages.

The blind man himself walked to the border the very next morning. He took Tanganyika Street. The pavement was dry enough to clap beneath his hard-soled shoes again, and he did not have to listen so carefully for the conversations of other people and the carrying sounds of the traffic. He could hear his steps rising up off the ground, hear them echoing against the walls and the fences. That was all the guidance he needed.

He knew immediately when he had reached the margin of the city. Behind him some kids were listening to music, singing along with excited little whoops and hollers. A pretzel vendor's cart was perfuming the air, as were the thousands of blades of grass that had opened up beneath the treads of so many shoes. Before him, though, there was a total cessation of both sound and smell. It was as though a wall had risen up in front of him, but a wall with none of the usual physical properties of a wall. When he tried to touch it, he encountered no resistance whatsoever. Before he knew it, he was reaching across his own chest, his hand a full foot to the left of where it had started.

The same thing happened when he tried a second time, and again when he tried a third.

The wall was intangible but impassable.

No wonder the birds had come flooding into the air, he reflected. They had no place else to go.

He followed the same road on his way back that he had on his way out, though the walk went more quickly now that he knew the obstacles and could place his feet on the ground with more confidence. Soon he was back in his own neighborhood. He passed through the thousand dangling fingers of the willow tree that stood outside the abandoned library, and then past the upright mailbox, and then, after he had crossed the street, beneath the high rectangular buzzing of the movie theater's marquee. The theater showed only old silent movies – classics – which was why the ticket vendor always refused to provide him with a ticket, though the blind man had explained a thousand times that what he enjoyed was not the movies themselves, but the cool air and the quiet flickering of the film as it unspooled and the great sense of space above his shoulders, almost enough space for a sky to form there, he imagined, with clouds and wind currents and its own systems of weather. Or perhaps he had failed to explain it a thousand times, or explained it only in his head, or explained it to someone else altogether. It was one of the deficits of old age that he no longer remembered many of the things he would have expected himself to remember.

And then there were the things he remembered in spite of himself.

A girl was skipping rope in the courtyard across the street from him, for instance, chanting a crossbred version of a rhyme that had been popular when he was a child: "Hamburger, fish sticks, quarter pound of french fries. Icy Coke, milkshakes, on Sundays it's an apple pie."

He winced as the rope slapped the ground, involuntarily recoiling. It took him a moment to figure out why. At first he thought it might have been because of the way the sand had lashed at him while he was crossing the desert, hissing like a snake, which was itself a kind of rope, a living rope, which passed through his fingers like nylon and made only the barest rustling sound as it touched the grass. A rope was like a whip, and it was only natural for a person to wince at the sound of a whip, even a person who had never been beaten. He himself had been beaten once, though not with a whip. But that had been so long ago and he was so much older now that he found it hard to believe it could have anything to do with his reaction.