Water burbled up inside it. He could see the ripples of movement, feel the change in weight when he lifted the flask again. Slowly, he poured it out into the puddle, then filled it again and poured it out once more. Again. Again. On his not-quite human face, a fairly-human expression of deep and pensive stillness grew.

This was useful. This was very useful.

There were no natural predators in the tunnels where his people lived (had always lived, to their way of thinking; Upworld was a big, bright nothing from which fell meat and branches and sometimes water, but not even Pool had yet considered that anything lived there). There had always been enough for Pool’s small clan to eat, and while very occasionally they might kill each other (in fits of rage, like the kind that sometimes took hold of Edges, or out of a certain confused resentment, of the sort which had compelled White Belly, the young female who shared Edges’ sleeping place, to pile furs over each of her previous infants when they would not stop crying and not take them off again until after the infants were very quiet and very, very still), it was not unusual for them to live a long time. Death came to them in the form of bloat-belly, the infrequent fall, the inexplicable and sudden collapse (as old Bent Thumb had done, with time enough for just one gasping rattle, one spastic grab at his own arm, and then he was just meat), and most of all, the fever.

The fever came in many forms, and every form was terrible. Fever might touch one of them and linger for days and days, or it might rip through all of them and be gone again almost at once. It could kill a man or let him live, chill his blood, take his sight or his hearing, gnaw his guts or his bones, or simply leave and do nothing at all. If it touched a child, that child died so often that sometimes the grieving mother went ahead and carried the limp and shivering body to the Pit and pitched it in as soon as the fever was identified. Flicker would have done that—twice—when little Glow caught the fever, had Pool not stopped her.

It was the sort of thing that made the others nervous, him stopping her. Bent Thumb never would have. Yes, he was leader, but Flicker was Glow’s mother. Pool had seen her born, yes, and many was the day he had spent crouched around that squirming, squeaking infant and nuzzling at her soft, round head, but that didn’t mean anything. All the same, when he’d seen Flicker take a dragging grip on little Glow’s unresisting ankles, he had not only leapt in front of her, but had slapped both hands down on the thick furs between them over and over until Flicker retreated and allowed Pool to crawl over the small girl’s body and press his own close.

He remembered that, and he remembered feeling that hot, dry flesh like a dead coal on his belly, and the agony of indecision that had gripped him every time before he had to leave her, to race down to the pool that had given him his name and suck up a mouthful of water to take back and dribble between her slack, chapped lips, expecting every time to come back and find her gone and Flicker at the mouth of the Pit. He never had, and Glow had recovered, but with this thing, this useful thing, he might have stayed with her the whole time, and fed the thirst that ravaged her wasted frame without ever leaving her side. Of course, Glow was much bigger now, not so reliant upon her mother, and perhaps in no great danger should the fever ever return, but there would be other fevers. This was a useful thing.

Pool, still deep in thought, brought the flask close to his face to watch the water well right up to the dark hole and out of it. The smell of Big Bill’s homebrew, diluted these past days, blew back at him, and he recoiled with a snort. His air blew across the mouth of the flask.

It made a sound.

Pool briefly succumbed to his ancestral instincts, dropping the flask at once and bashing at it with his fist. He darted back to the tunnel and looked back, poised atop his toes for flight, head low to the ground, hissing.

The flask lay open in the rain, somewhat dented, still shining.

After several long, motionless moments, Pool crept back, hand over hand. He stared the thing down, hissed twice, bashed it again, and finally, suspiciously, drew himself up to hunkers again and picked it up.

It was cool in his hands, unresisting. Not a person. Not even an animal. Just a thing.

Pool thought for a very long time.

Slowly, he brought it to his face again and deliberately snorted.

Nothing.

He shook it. Water sloshed and splashed inside. He snorted again, louder, then tried a chuff, a rattle, a whole series of snaps and grunts, and finally, a hoot.

The flask remained silent.

Edges was not the only one who could be overcome by temper. Pool yanked back his arm to throw it.

It made the sound again.

Pool stopped his arm at the apex of its swing and craned his neck around to look at it. He sat up a little straighter and swung his arm again.

The flask made its low groaning song at him.

Rain fell.

Pool thought.

He brought the stinking thing right to his lips and did not snort or hoot or chuff. He softly, silently, blew. Not into it. Across it.

The flask moaned.

All at once, the potential of the strange thing changed. Gone were thoughts of fevers and thirst and memories of little Glow’s body burning beneath his. He thought instead of Echo. Because this was very, very interesting.

It was difficult to find her, but Echo seemed to spend much of her time around the light places and there weren’t many of those. Pool found her while it was still light, and he stayed well back in the tunnels for a time, admiring her. She was beautiful, lean and young and strong. The light from Upworld made her skin gleam, as white in these tunnels as the fish that swam through the dark water that had given him his name. He watched her cup her hands for falling water and felt his groin tighten.

He made no sound, but she must have caught his scent because she stiffened suddenly and looked his way, sending out three clicks and one long rattle when those clicks sent back his shape. She dropped, slapping loudly at the wet ground and showing all her teeth, which were youth-sharp and as white as her flawless skin.

Pool realized all at once that he’d actually trapped her. The walls of the shaft that opened to Upworld were too steep and smooth to climb and there was no way out except to go past him—a tight, dangerous squeeze. He had her now. She was fast, but one lunge would have her.

Very slowly, very carefully, Pool eased a few steps closer to her and let the light from above fall on him. She hissed, spat, leapt scrabbling at the high walls, fell back onto the wet ground and spat again.

Pool ducked his head and softly purred as Echo paced before him, her hands and feet light and quick as they moved in the close opening. He watched, but from the corner of his eye. He did not stare, made no gestures, said no words, and gradually, gradually, her step slowed. She didn’t stop, but slowing was an encouragement.

Pool brought out the flask and placed it before him. Echo spat at it and at him and began to pace again, slapping her hands in frustration at the enclosing walls. Pool watched, purred, waited, and when she again began to slow, he brought the flask to his mouth and blew.

Echo did stop walking then, her eyes locked wide upon the strange, shiny object as it made its moaning song. Pool chuffed contentedly, soothingly, and blew again, then set the flask down and pushed it toward her.

Echo looked at it and at him. Her smooth brow crinkled.

“Pool,” said Pool.

She rattled again, but it seemed uncertain to his ears. Heartened, he hunkered low. She sprang up. He rolled onto his side to look a little less predatory and able to leap, and she began to pace again, her eyes coming back to the flask again and again.