She was half convinced that the faraway sounds she had been hearing since shortly after she left Chris and Valiha were echoes of her own footsteps, the faint whispers of glowbirds shifting on their perches, the distant sounds of falling water. But being half convinced leaves a lot of room for the imagination, and the picture of the Night Bird had leaped from her childhood memories to shriek and gibber just out of her sight.

She did not believe it was the Night Bird; even in her present state she knew no such animal had ever existed, either here or on Earth. It was a story little girls told each other and nothing more. But the thing about the Night Bird was that no one ever saw it. It swooped down on wings of shadow and always attacked from behind; it could change its size and shape to conform to whatever dark place was available, hiding with equal ease in a gloomy cubicle, under a bunk, or even in a dusty corner. Whatever was trailing her-if there was anything-seemed to belong to that dreamworld.

She saw nothing. From time to time she thought she heard the sound of claws snapping together, the rattle of a ghastly beak.

Robin knew there were more living things in the cavern than the glowbirds, the cucumbers, shrimp, and lettuce, and the various plant species. There were tiny glass lizards with from two to several hundred legs. They liked heat and had grown more abundant as she moved east, so that her first morning chore was to rid her sleeping bag of the ones that had crept in. There were things like starfish and snails with shells as varied as snowflakes. Once she had seen a glowbird in flight snatched away by some unseen flier, and another time she had found something that might have been part of the ubiquitous body of Gaea denuded of her rocky covering, or could as well have been a creature beside which a blue whale would have seemed no more than a minnow. All she knew for sure was that it was warm and fleshy and, luckily, somnolent.

If all these things lived in a cavern that was, at first glance, endless kilometers of rocky sterility, why not the Night Bird?

Once more she tried to look over her shoulder, this time succeeding in lifting her chin a little. Soon she was able to twitch her feet. But long after she could move her legs and arms, she remained perfectly still, her feet almost a meter lower than her head, to be sure she was completely in control before she dared try to move from the slope where she had fallen.

When she did move, it was with infinite caution. She edged backward on her heels and elbows until she felt the ground leveling out, then turned to hug the warm rock. Gravity was a wonderful thing when it was pressing you down against a stable surface, not so nice when it tried to pluck you from an uncertain perch. She had seldom thought about gravity before, as either friend or foe.

When her trembling stopped, she crept to the edge of the ravine where she had lain helpless for so many hours. One of her glowbirds had been crushed beneath her when she fell. The other was flickering, near death, but it cast enough light for her to look down and see the bottom, no more than a meter and a half from where her feet had been.

When she came to Gaea, she would have laughed at such a distance. She did not laugh now. After all, it did not take a hundred meters to kill; it did not even take ten. One or two would do, if she hit right.

She took stock of first her body, then her equipment. There was a sharp pain in her side, but after careful probing she decided no ribs were broken. There was blood dried under her nose; she had smacked it when her legs gave way, just before starting her terrifying, feet-first slide into the unknown. Aside from that and some scrapes and a torn fingernail, she was all right. An inventory of the equipment she had kept after several episodes of weeding revealed nothing missing. Her glowbird cage was crushed, but she no longer had any animals to keep in it, and she could make a new one from reeds and vines at her next camp.

She had lost track of how many times she had brushed disaster, was to some degree unsure of just what counted as a brush. Even if she eliminated all the times she had felt her hands slipping on the rope, the momentary losses of footing, the falling rocks that hit only a few meters away, the quicksand that turned out to be only waist-deep, the flash flood that came from nowhere and thundered through a gully she had been about to cross ... even if she counted only the times she had actually felt the grasp of death as a cold, malefic presence, as though its clammy hand had brushed her and left its spoor of fear on her soul, it was too many times. She was lucky to be alive, and she knew it. There had been a time when danger exhilarated her. That time was no more.

Each day brought its new fear. There were so many by now that she was no longer even ashamed of them; she was too beaten down, too crushed by the collapse of the person she had thought herself to be. If anyone ever emerged from this cavern, she knew it would not be Robin the Nine-fingered but some subdued stranger.

It had not been easy to be Robin, but she was a person to respect. No one had ever pushed her around. Once again she wondered why she kept on. It would be more honorable, she felt, to live her life here where no one could see her. To emerge into the light would be to expose her shame.

But sometime later, urged on by a force she did not understand and would have resisted if she had known how, she got up and resumed her long walk east.

It had seemed so simple when she explained it to Chris and Valiha. She would make her way through the cavern, heading always toward the east, until she reached Thea. Of course, that was assuming the direction they were calling east really was east, but if it wasn't, there was little she could do about it.

But it soon became apparent she would have to make more leaps of faith than that first, basic one. She had to assume that the cavern, which was one or two kilometers across at the west end and reached into the unguessable east, would keep going in that direction. And there was no reason to assume that. By the pinpoint lights of the glowbirds she was able to tell the general trend of the passage for two or three kilometers in each direction. It seemed to average out as a straight line, but there were so many twists and curves she could not be sure.

There was another possibility. It was impossible to tell if the cavern was rising or descending. They had started at a level she knew to be five kilometers beneath the surface because Cirocco had said so. She also knew Gaea's outer skin was thirty kilometers thick. There was room to miss Thea's chamber by quite a margin.

Two simple instruments could have banished her disorientation. To go up in Gaea was to become lighter, while descending would have made her weigh fractionally more. A sensitive spring scale could have measured those differences. Her own senses were inadequate. The gyroscopic Gaean clock could have been used as a compass because when its axis was oriented north and south, it no longer turned. By aligning the clock until it stopped and then turning it ninety degrees, she could learn east and west by whether the clock ran backward or forward. But neither Gaby nor Cirocco had ever needed a spring scale in her travels, so they had not packed one. And the clock had stayed with Hornpipe.

She wasted a great deal of time trying to fix her position and direction using simple equipment, and ended up being completely baffled. In particular, it should have been possible to determine east and west by the behavior of falling objects. She tried setting up long plumb lines and dropping things, with inconclusive results. So in the end she blundered on, lost in the dark. She had been doing it for at least three kilorevs, possibly more. She followed the north wall. It had seemed a good idea until she came to the end of a passage, no more than twenty sleeps into her trip. She had followed the south wall back until it began to bend and kept bending through 180 degrees, and she realized she had entered a side passage without knowing it. There was nothing to do but go back across the passage until she reached the marks she had made to guide Chris and Valiha, cross out one and chisel in a new one, directing them to the other passage. Until it, too, ended abruptly three sleeps later.