“Good to meet you,” he yelled up. “I’ve got a proposal for you. Any chance we could have a chat?”

The three garuda looked at each other.

“What you want?” yelled the black-feathered one.

“Well, look—” Isaac gesticulated at the crowd “—this isn’t really how I was envisaging this discussion. Is there anywhere private we could go?”

“You bet!” said the first one. “See you up there!”

The three pairs of wings boomed in concert and the garuda disappeared into the sky, leaving Isaac wailing behind them.

“Wait!” he shouted. It was too late. He looked around for the guide.

“I don’t suppose,” Isaac asked him, “the lift’s working in there, is it?”

“Never got put in, squire.” The guide grinned wickedly. “Best be getting started.”

“Dear sweet Jabber’s arse, Lin . . . go on without me. I’m dying. I’m just going to lie here and die.”

Isaac lay on the mezzanine between the sixth and seventh floors. He hissed and wheezed and spat. Lin stood over him, her hands on her hips with exasperation.

Get up, you fat bastard, she signed. Yes, exhausting. Me too. Think of the gold. Think of the science.

Moaning as if he were being tortured, Isaac staggered to his feet. Lin chivvied him to the edge of the concrete stairs. He swallowed and braced himself, then staggered on up.

The stairwell was grey and unlit except by light filtering round corners and through cracks. Only now, as they emerged onto the seventh floor, did the stairs look as if they had ever been used. Rubbish began to build up around their feet. The stairs were grubby rather than thick in fine dust. At each floor were two doors, and the harsh sounds of garuda conversations were audible through the splintered wood.

Isaac settled into a slow, miserable pace. Lin followed him, ignoring his declarations of imminent heart attack. After several long, painful minutes, they had reached the top floor.

Above them was the door onto the roof. Isaac leaned against the wall and wiped his face. He was drenched in sweat.

“Just give me a minute, sweetheart,” he murmured, and even managed to grin. “Oh gods! For the sake of science, right? Get your camera ready . . . All right. Here we go.”

He stood and breathed slowly, then strode slowly up the last flight to the door, opened it and walked out into the flat light on the roof. Lin followed, her camera in her hands.

Khepri eyes needed no time to adjust from light to darkness and back again. Lin stepped out onto a rough concrete roof littered with rubbish and broken concrete and saw Isaac desperately shielding his eyes and squinting. She looked coolly around her.