“De Bonneville, why did they send you back here?”

“I have a propensity for offending the Kabaka, Malenfant, most efficiently and with the minimum of delay. So here I am again.”

“You’re a prisoner?”

“In a way. The guards ensure that the workers are kept here until such time as the Kimera sickness takes hold of their limbs and complexion. Then one is free to wander about the town without hindrance.” He touched his blackened cheeks; a square centimeter of skin came loose in his fingers, and he looked at this latest horror without shock. “The stigmata of Kimera’s punishment are all too obvious,” he said. “None will approach a yellow-cake worker, and certainly none will feed or succor him. And so there is no alternative, you see, but to return to the Engine, where at least food and shelter is provided, there to serve out one’s remaining fragment of life…”

“Who is Kimera?”

“Ah, Kimera!” he said, and he threw back his ravaged head. Kimera, it turned out, was a mythical figure: a giant of Uganda’s past, so huge that his feet had left impressions in the rocks. “He was the great-grandson of Kintu, the founder of Uganda, who came here from the north; and it was Wanpamba, the great-great-grandson of Kimera, who first hollowed out the hill of Rubaga and entombed the soul of Kimera here…” And so forth: a lot of poetical, mythical stuff, but little in the way of hard fact. “You know, they had to reconstruct these old myths from the last encyclopedias, for the people had forgotten them — but don’t let the Kabaka hear you say it…” De Bonneville’s eyes closed, and he sank back, sighing.

Nemoto, nervous, plucked at Malenfant’s sleeve. Her mime was obvious. Time was up; they should go; this was an unhealthy place.

Malenfant didn’t see what choice he had. All the way out, Malenfant was aware of de Bonneville’s gaze, locked on his back.

Outside the grisly dormitory, Malenfant peered into the deeper blackness of the well. “Nemoto, what’s down there?”

“Danger. Death. Malenfant, we must leave.”

“It is the Engine of Kimera, whatever the hell that is. You know, don’t you? Or you think you know. Rubaga has the only significant radiation-anomaly signature on Earth…”

Her face was as expressionless as her Moon-rock Buddha’s. “If you want to fry your sorry skin, Malenfant, you can do it by yourself.” She turned and walked off, leaving him with the guard.

The guard looked at him quizzically. Malenfant shrugged, and pointed downward.

He walked to the ledge’s rim — a sheer drop into darkness, no protective rail of any kind — and leaned over. There seemed to be a breeze blowing down from above, rustling over the back of his neck, into the pit itself, as if there were a leak in the world down there. Now, he couldn’t figure that out at all. Where was the air going? Was there a tunnel, some kind of big extractor?

The only light came from the flames of rush torches, flickering in that downward breeze, and Malenfant’s impressions built up slowly.

He made out a large heap of ore, crushed to powder, contained within a rough open chamber hollowed out of the stone. Maybe that ore was the yellow-cake de Bonneville had talked about. Long spears of what appeared to be charcoal — like scorched tree trunks — stuck out of the heap from all sides and above. Water was carried in channels in the walls and pipes of clay, and poured into the heart of the heap. He guessed the heap contained a hundred tons of yellow-cake; there were at least forty charred trunks protruding from it.

The chamber was full of people.

There were a lot of tall Uprights, many squat habilines, and some Waganda: men, women, and children who limped doggedly through the darkness, intense heat, and live steam, serving the heap as if it were some ugly god. They hauled at the charcoal trunks, drawing them from the yellow-cake, or thrust them deeper inside. Or else they hauled simple wheelbarrows of the yellow-cake powder to and from the heap, continually replenishing it. Their illness was obvious, even from here. Peering down from far above, it was like looking over some grotesque anthill, alive with motion.

The heap was intensely hot — Malenfant could feel its heat burning his face — and the water emerged from the base of the heap as steam, which roared away through a further series of pipes. There was a lot of leakage, though, and live steam wreathed the heap’s ugly contours.

The principle was obvious. The heap was an energy source. The steam produced by the heap must, by means of simple pumps and other hydraulic devices, power the various gadgets he’d witnessed: Mtesa’s ascending throne, the fountains. Maybe the water that passed through the system was itself pumped up from some deeper water table by the motive power of the steam.

There had to be a lot of surplus energy, though.

And now he made out a different figure, emerging from some deeper chamber at the base of the pit. It was a woman. She looked like a cross between a habiline and an Upright: big frame, thick neck, head thrust forward. She was wearing a suit, of some translucent plastic, that enclosed her body, hands, and head. She was familiar to him, from a hundred TV shows and school-book reconstructions. She was Neandertal: another of humanity’s lost cousins.

Holy shit, he thought.

There was a flash of light from the hidden chamber, from some invisible source.

It was blue, a shade he recognized.

Neandertals, and pressure suits, and electric blue light. Unreasoning fear stabbed him.

He got out of there as fast as he could.

The next day Malenfant visited de Bonneville again. Malenfant brought him a small bottle of pombe; de Bonneville fell on this avidly, jealously hiding it from the other inmates of the ward. Malenfant wanted to ask about the Engine, but de Bonneville had his own tale to tell.

“Listen, Malenfant. Let me tell you how I came to this pass. It started long before you arrived…”

De Bonneville told him that a gift had arrived for Mtesa, the emperor, from Lukongeh, king of the neighboring Ukerewe. There had been five ivory tusks, fine iron wire, six white monkey skins, a canoe large enough for fifty crew — and Mazuri, an Upright girl, a comely virgin of fourteen, a wife suitable for the Kabaka.

“Mtesa’s harem numbers five hundred. Mtesa has the pick of many lands; and many of the harem are, as I can testify, of the most extraordinary beauty. But of them all, Mazuri was the comeliest.”

“I think I saw her in the palace. Mtesa likes her.”

“She has—” De Bonneville waved his damaged hands in a decayed attempt at sensuality. “ — she has that animal quality of the Uprights. That intensity. When she looks you in the eyes, you see direct into her primeval soul. Do you know what I’m talking about, Malenfant?”

“Yes. But I’m a hundred years old,” Malenfant said wistfully.

“Mazuri was young, impetuous, impatient at her betrothal to Mtesa — a much older man, and lacking the vigor of her own kind…”

De Bonneville fell silent, in a diseased reverie.

“Tell me about the Engine.”

“The Waganda say the yellow-cake is suffused with the Breath of Kimera,” de Bonneville said, dismissive. “It is the Breath that supplies the heat. But a given portion of yellow-cake is eventually exhausted of its Breath, and we must extract and replace the cake, continually.”

“What about the tree trunks?”

“We must insert and extract the trunks, according to the instructions of—” He quoted a term Malenfant didn’t know, evidently a sort of foreman. “The Breath is invisible and too rapid to have much effect — except on the human body, apparently, which it ravages! The tree trunks are inserted to slow down the Breath from the heart of the heap. Do you see? Then it gets to work on the rest of the yellow-cake. And that is, in turn, encouraged to produce its own Breath in response. It’s like a cascade, you see. But the Waganda can control this, by withdrawing their charred trunks; this has the effect of allowing the Breath to speed up, and escape the heap harmlessly…”