But now her vision seemed to be failing. The Air was growing poor at carrying the high-frequency, high-velocity sound waves which allowed her to see. And, worse, the Air — thin as it was — was losing its superfluidity. It started to feel sticky, viscous; and as she moved she began to feel a breeze, faint but unquestionably present, plucking at her face and hair-tubes, impeding her motion.

She found herself trembling at the thought of this sticky stuff congealing in the fine network of capillaries which powered her muscles — the network which sustained her very being.

Human Beings weren’t meant to live up here. Even pigs spent no more time close to the Crust than they had to. She heaved at the sludgelike Air, feeling it curdle within her capillaries, and longed for the open space of the Mantle beneath the roof-forest, for clean, fresh, thick Air.

In all directions around her the tree trunks filled the world. As it became progressively more difficult to see, the trunks, parallel, curving slightly to follow the Magfield, seemed suddenly artificial, sinister in their regularity, like the threads of some huge Net around her. She found herself gripped by a slow panic. Her chest heaved at the unsatisfying Air, the breath noisy in her throat. It took a strong, conscious effort to keep moving, an exercise of will just to keep her hands working at the tree trunk.

She was concerned for Farr. Even in the gloom she could see how distressed he was: his face was white and seemed to be bulging, his eyes half-closed; he seemed barely aware of where he was, and he moved along the trunk stiffly.

Dura forced herself to look away, to carry on. There was no help she could give him. Not now. The best she could do was to move on, to bring home the results of a successful hunt. And as Adda had said, the boy was probably safer with her than anywhere else…

At least Adda was close to Farr. Dura found herself offering up a simple, childlike message of thanks to the watchful Xeelee for the old man’s presence and support.

When the climb ended it was with a suddenness that startled her.

The tree trunk she’d followed had broadened only gradually, at last reaching a width just too great for her to stretch her arms around. Now, suddenly, the clean lines of the trunk exploded into a complex tangle of roots which formed a semicircular platform over her head. Peering up, she could see the roots receding into the dim, translucent interior of the Crust itself; they looked almost like human arms, reaching deep into the gossamer solid in search of neutron-rich nuclei of molybdenum, strontium or krypton.

Looking around, she saw how the root system of the tree merged with those of its neighbors in the forest, so that a carpet of wood formed an impenetrable ceiling over the forest. A few strands of purplish grass sprouted among the roots. The tree trunks, following the Magfield lines, met the root ceiling at an oblique angle.

Soon the others had joined her. The four Human Beings huddled together, clinging to loose roots for stability. It was so dim now that Dura could barely make out the faces of her companions, the outlines of their thin bodies. Philas’s eyes were dull with exhaustion and apathy; Farr, trembling, had his arms wrapped around himself, and his mouth was wide as he strained at the residual Air. Adda was as uncomplaining as ever, but his face was set and pale, and Dura could see how his old shoulders were hunched over his thin, heaving chest. Adda took leaves from the bulging pack at his waist. Dura bit into the food gratefully. Insubstantial and unsatisfying as it was, the food seemed to boost what was left of her strength. Farr continued to shiver; Dura put an arm around him and drew him closer to her, hoping to transmit enough of her body warmth to stop the trembling.

Farr asked, “Are we at the Crust?”

“No,” Adda growled. “The true Crust is still millions of mansheights above us. But we’ve reached the roots; this is as far as we can go.”

Philas’s voice was low and harsh in the thin Air. “We can’t stay here for long.”

“We won’t need to,” Dura said. “But maybe we should open up a trunk and start some nuclear burning again, before we congeal here. Adda, could you…”

The old man raised a hand, curtly. “No time,” he breathed. “Just listen… all of you.”

Dura frowned but said nothing. The four fell into a silence broken only by the rattle of their uneven breaths. Dura felt small, vulnerable, isolated, dwarfed by the immensities of the root systems over their heads. Every instinct ordered her to bolt, to slide back down the tree and plummet through the wall of treetops to the open Air where she belonged; and she could see the same urges in the set faces of the others.

There. A rustle, a distant grunting… It came from the root systems, somewhere to her left.

Adda’s face crumpled with frustration. “Damn it all,” he hissed. “I can’t hear; my ears are turning to mush.”

“I can hear them, Adda,” Farr said.

Dura pointed. “That way.”

Adda nodded, his good eye half-closed with satisfaction. “I knew it wouldn’t take long. How many?”

Dura and Philas looked at each other, each seeking the answer in the other’s face. Dura said, “I can’t tell, Adda… more than one, I think.”

For a few seconds Adda swore steadily, cursing his age, his failing faculties. “Well, into the Ring with it,” he said finally. “We’ll just have to chance there aren’t too many in the herd.” In an urgent, harsh whisper he gave them careful instructions on how, in the event of attack by a boar, they should scatter… and work across the Magfield flux rather than try to flee along it. “Because that’s the way the boar will go. And, believe me, the boar will be a damn sight quicker than you.” His face was a murderous, chilling mask in the twilight.

Dura said, “Philas, go with Adda and Wave around to the far side of the herd. Take the nets and rope and get downflux from them. Farr, stay with me; we’ll wait until the others are in position and then we’ll chase the pigs into the nets. All right?”

Hurriedly they passed around the equipment they would need. Dura took two short stabbing spears from the bundle carried by Philas. Then Adda and Philas slid silently into the darkness, working across the Magfield by Waving and by clambering across the parallel tree trunks.

Farr stayed close to Dura, still pressed close to her for warmth, trusting. For a few seconds she looked down at him — his eyes seemed vacant, as if he were not fully conscious — and she tried to imagine how she would feel if anything were to befall this boy, as a result of her own ignorance and carelessness.

Well, she thought ruefully, at least she’d done her best for him in the way she’d structured the hunt. It was undoubtedly safer to be upflux of the herd when the hunt started. And she would have been greatly more worried if she hadn’t stayed with Farr herself.

With a last, brisk hug, she whispered, “Come on, Farr. We’ve got work to do. Let’s see how close we can get to those pigs without them spotting us.”

He nodded dully and drew away from her, still shivering.

Hefting a short spear in each hand, Dura began to pull herself across the lines of the fat trunks in the direction of the noises she’d heard. Moving in this direction, the resistance of the Magfield was added to the thickened viscosity of the Air, and the going was hard. She felt submerged and had to suppress a pang of panic at the feeling of being trapped up here, of being unable to free herself from this solidifying Air.

She did not look back, but was aware of Farr following her, perhaps a mansheight behind; he moved silently save for his rattling breath, and she could hear how he was trying to control the noise of his breathing. The brave little hunter, she thought. Logue would have been proud of him.