Laura could see the woman sitting in her car. She was still holding the telephone to her cheek. Her knuckles were as white as candle wax.

"Mom," Laura asked, "why is she squeezing that phone so hard?"

Then the woman began to cry.

As they waited for the police, the school's front drive became crowded with the cars of all the parents and child-care workers who were lining up for the three-fifteen bell. The sunlight reflected off their windshields, hubcaps, and bumpers, filling the air with knives.

After a while, Laura began to feel an ache in her muscles from the impact of the crash. She unbuckled her seat belt, rested her head on her mother's lap, and stared at the ceiling.

"Well, it looks like we'll have to reschedule your dentist's appointment, hon," her mother said.

"Oh, that's right," said Laura. "I forgot all about it."

And when the sirens came, she didn't know whether they were the police cars pulling into the lot or those other sirens, the ones that sounded when the bombs were going to fall, the sirens of the orange vests.

It took her six more days to make it through the pass onto the Ross Ice Shelf. Six days of continuously falling snow that spun through the air in nets and skeins and lashes. Six days of collapsing ice and stone embankments that rose up inside the storm like baited traps. She had been afraid that she would miss the gap altogether, veering off the path and dead-ending against the side of the mountain, but she woke up one morning to an unexpectedly full silence, and when she stepped outside she found a plain of unblemished white ice stretching into the distance before her. Her relief was immense. The weather must have cleared while she was asleep. She turned around to see a line of cliffs and the tongue of the ice stream behind her. Immediately she understood what had happened: she had cut through the notch the day before, without even realizing it.

She packed the sledge quickly in the rising light and set out again. If the weather persisted – and that was quite an "if" so close to the coast – she might reach the station before exhaustion finally took hold of her. But conditions could change at the snap of a finger, and she wanted to cover as much distance as she could before they did.

Soon the sledge was traveling so swiftly that twin arcs of snow shot out from beneath the runners, pattering onto the ice with a quiet slapping sound. As the noon hour approached, the sunlight shone from off the snow as if from a layer of pressed foil. Beneath the sledge was the ice, and beneath the ice was the ocean, and she was surprised that she couldn't feel the circulation of the water down there. She had thought that she would be able to. But the shelf ice seemed just as solid, just as anchored, as the continental ice had been. Of course, the continental ice wasn't nearly as impermeable as it had been a few decades ago, before the great melting began. And from the little – very little – geology she had studied, she knew that even the land itself was never as stable as it seemed. Beneath the glaciers, after all, was the stone, and beneath the stone was the magma, and no matter where you stood on the planet, you were always bobbing around like a cork in open water. Perhaps she had just gotten used to the feeling.

Every time she climbed out of the sledge, and every morning when she left the jacketing warmth of her tent, the vigor of the cold would make her catch her breath. How long had it been since she'd set out from the shelter? Two weeks? Three? Already the days had become colder. The string that bound the sun to the horizon had grown shorter. She would make it through six or seven hours of sledging before the darkness settled over the ice – maybe eight hours if there were a few low-hanging clouds along the skyline to reflect the final traces of the light. Then she would erect her tent and go to sleep. The GPS system was working again, and if she wanted, she could have driven through the night, guided by the khaki-colored markings on the monitor. But she was tired. And beyond that, she was afraid. She was afraid that she would reach the station and somehow fail to see it.

She kept thinking about the time shortly after she graduated from college when she drove home from a late-night party and woke up on the front lawn of the house she shared with her boyfriend. She had spent the night sleeping in her car. Its fuel cell was depleted, but the front lights were still burning, and a group of children were standing above her tapping on the window. "I'd get out of here if I was you," one of them said when she opened the door, a boy with a globe of frizzy red hair. "The guy who lives in that house is an a-s-s-hole." Which, as it later turned out, he was. She had spent the next few weeks wondering what had happened to her. She remembered struggling to stay awake, then turning onto her street with a sense of exquisite relief, but after that nothing at all. She was amazed that she hadn't folded the car around a tree or a streetlamp. Or a camper van or a swing set or a living room. It was possible to drift without thinking into what you were looking for, but it was just as possible to drift right past it into something far worse. She must have come to a stop on her own front lawn by nothing more than the purest luck.

Sometimes, as she traveled across the ice shelf, the sky would gray over and the snow would begin to fall again, but it never lasted for long. Though there were mornings when she woke to find the tracks her sledge had left in the ice obscured by a covering of fresh powder, there were just as many mornings when they were lit to a razor's sharpness by the brightening sun and she could see them extending into the distance like carvings on a wax tablet.

Once, after a night of soft but persistent winds, she found the ground outside her tent scattered with thousands of marble-sized balls of snow. They were lined up along the sheltered side of the ridges, and were so delicate that they collapsed into a heap of crystals the second she touched them. She had never seen anything like them. Even the vibration of her footsteps was enough to make them collapse, she discovered, so she tried not to step too close to them.

Tried not to kill them, was how she thought of it. In the past few weeks, ever since Puckett and Joyce had left, everything around her seemed to have developed a personality.

By the time she loaded the sledge, the breeze had changed direction slightly, lifting the balls out from behind the ridges. They went skittering away across the shining field like mice. She powered up the sledge and started out toward the northwest.

She knew that she must be getting closer to the rim of the ice shelf. Fissures and crevices were appearing in the ice more and more frequently now. She slowed down whenever she saw a gap approaching, easing over it until the flippers caught on the other side and she was sure she could move forward. Once or twice she felt the balance of the sledge tipping over and had to back up and change course until the break narrowed.

At the bottom of one of the fissures, she spotted a dark thread of water. A few minutes later, an egg-shaped opening appeared in the ice, and she stopped the sledge to peer over the edge. There was a sunken pool of water inside, some ten feet down, telescoped by the walls of the tunnel. She could see it rising and falling, lingering for a few seconds at either end like the pectoral muscles of a sleeping giant. It was the ocean. She was sure of it. She was at that margin where the shelf ice began to break apart into pack ice, separating into mile-long chunks that bumped into one another as the currents tugged them back and forth. The station couldn't be more than a day or two away.

She moved out again with a renewed intensity. The few clouds that had been in the sky at dawn were gone now, and the air was scrubbed clean, so transparent that it played tricks with her notions of distance. Late in the afternoon, she saw a faraway structure with the low roof and squared off walls of the station, and her heart began to race. She accelerated toward the building, but suddenly it was gone. She activated the magnification feature on her windshield, but still she couldn't see it. She climbed down from the sledge to take a look around. Half a dozen steps behind the left runner she found the object she had seen. It was a juice box. A juice box with the low walls and squared off roof of the station. The familiar red and white Coca-Cola wave was slinking across the front, and the C. C. Juice slogan was printed just beneath it: "The Great Taste of Cola… in a Juice!" Somebody must have dropped it traveling across the ice shelf. One of the scientists from the station, maybe. Or Puckett or Joyce.