As they started running east, Swan howled over the common band, a sound like an alarm siren that had done its duty but continued on in the emptiness after a disaster. The figure running before him did not seem capable of generating such a terrible sound, which stuck him like pins in the ears. A lot of animals had no doubt been left behind inside—the whole little terrarium, a community of plants and animals. And she designed such things. And this one was her home. Suddenly her howl made it clear to him that saving the humans of the place was not really enough. So much got left behind. A whole world. If a world dies, its people don’t matter anymore—so the howl seemed to say.

Dawn kept coming, as always.

Now this was an interesting matter: could he modulate his fear, rein it in and use it to impel him at the optimum pace for the quickest arrival at the platform out there to the east, in the raw light of daybreak? And did that pace match the pace that was going to be set for him by the person he was following? For Swan was moaning still, crying and cursing, keening in a rhythm that was keyed to her running; she bounced forward on the impact of her strides, perhaps helpless to go slower; and yet she was moving faster than he could match. He had to give ground and keep to his own pace, and hope that he would at least be able to keep the distance close enough that he wouldn’t lose her over the horizon. Although of course the tracks would lead him right to the platform, so even if she disappeared over the horizon, that should not matter. And yet he did not want to lose sight of her. The three sunwalkers were already a considerable distance ahead of her, even the one with the hurt arm. So maybe the unhappy noise she was making was in fact slowing her down.

The land dipped and rose here in such a way that he could see many kilometers to the north, and the highlands in that direction were now all ablaze with sunlight. That lit part of the landscape threw light over the shadowed terrain they ran in, and Wahram saw the rumples in the land, and the rubble on it, better than he had ever seen anything before, not just on Mercury but anywhere. Everything looked coated by a layer of friable powder, no doubt the result of the daily bake and freeze.

The light from the north grew so bright he had to look away to preserve his vision for the dark places underfoot and before him. Ahead the moaning silhouette bounded against the stars. He forced his breath into a rhythm with his feet, watched the ground he was running on, focused on a rapid efficient gait. One-third g could be deceptive, being neither light nor heavy. It had the potential for speedy running, but a fall was not a trivial thing, especially in this situation. Swan was on home ground and did not appear to be thinking of him at all.

He ran on. Normally the distance involved would be for him a matter of about forty-five minutes of running, he reckoned, depending on terrain. That was long enough to call for restraint from full speed, even for runners. Was she going out too fast? He saw no signs of deceleration.

On the other hand, she was not getting farther ahead. And he was now in a pace he thought he could sustain. It was neither fast nor slow. He huffed and puffed, watched the ground carefully. Quick glances showed Swan always well short of the horizon. It was all going to work out—then he stumbled and had to catch himself up by way of some desperate windmilling of the arms, after which he kept his head down and focused on the ground more than ever.

It was one of those moments when the shock of the unexpected throws one into a different space. He could see Swan’s boot prints superimposed on the palimpsest of earlier prints. Her stride was shorter than his. He flew over her steps, even though he was losing ground on her. The sunwalkers were halfway over the horizon. Swan’s moaning still filled his ears, but he refused to let himself turn down the volume or turn it off.

Then the sun blinked over the horizon, and again he felt his heart pounding. At first, licks of orange fire popped over the horizon and disappeared. The corona was hotter than the actual surface of the sun by a great deal, as he recalled. Magnetic surges, bowing up in characteristic loops of fire, rising majestically over the horizon and hanging there before blasting off to one side or the other. The sun’s flames, in effect, flying up in stupendous explosions guided by the magnetic fields that roiled in the burn. He ran on looking down at the ground, but the next time he glanced up most of the horizon ahead of him was orange—the sun itself, its orangeness stuffed and writhing with bubbles and banners of yellow. To stop it down to something his eyes could handle, his faceplate had to render the rest of the cosmos black. The horizon was the only thing that could be clearly picked out, a line out there not very high, not smooth, various hills and dips that bounced and blurred. Swan stood out blackly, a runner imago, her silhouette thinned by white light pouring around her. The ground underfoot was now a salt-and-pepper pattern impossible to read, aching white and deep black all jumbled together so that the white parts pulsed and shimmered in his vision. He had to trust it was flat enough to run, because it didn’t look like it. And then after another while it became a black-chipped white that looked flat as a sheet. They were out in full day.

He began to sweat. Probably this was just fear, and the sudden helpless acceleration in his pace. His suit began to hum audibly in its effort to cool him, a slight but terrible sound. His sweat would slide down his flanks and legs and collect at a seal above the boots. He didn’t think enough could collect to drown him, but he wasn’t sure. The black flicker of Swan in the sun had become a sort of spectre of the Brocken, exploding in and out of existence in vibrant pulses. He thought he saw her look over her shoulder at him, but he did not dare wave to her lest he lose his balance and fall. She seemed short, and suddenly he saw she was visible now only from the knees up. The horizon was about as far away as it would be on Titan. That meant he was probably only five or ten minutes behind her.

Then the platform top appeared over the horizon just to her left, next to the southernmost track, and he quickened his pace yet again. In any physical endeavor a little kick at the end could usually be found.

This time, however, it seemed he was truly stretched to his maximum. Indeed it very quickly turned into something more like a desperate attempt to hold what speed he had. He was gasping, and had to force himself to a breath pattern in a rhythm coordinated with his pounding heavy legs, one gasp for two strikes. It was very frightening to look up and see almost the whole visible stretch of the eastern horizon topped by the corona; the slight curve of it seemed to suggest it would eventually fill most of the sky, as if what was rising before them was some kind of universal sun. Mercury looked like a bowling ball rolling into that light.

His sweat now filled his suit to his thighs, and he wondered again if he could drown in it. But then again, he could drink it and save himself. Happily his air supply was still cool in his face.

His faceplate polarization shifted, and the texture of the sun through the black glass of his faceplate articulated into thousands of tongues of flame. Big fields of tendrils moved in concert, whole regions swirling like cats’ paws on water. It looked like a living being, a creature made of fire.

The platform was a block of black in the black, Swan a black movement beside it. He reached her, stopped, gasped for a while with his hands on his knees, his back to the sun. Her keening had stopped, although from time to time she still moaned. The sunwalkers apparently had already taken the elevator down; she was waiting for it to come back up.