"It fell in the water next to the waterfall. It was switched on. She may be able to see it from the gantry. "

"Oh, Rabbit. If they come back down the ladder, we're going for the water. "

"Can they catch us?"

"Raffmir may be able to reach us with gallowfyre. If he can, we're lost."

We stayed still, the strange shifting light exaggerated by the reflections from the roiling water. The warm heartbeat of the stone against my breastbone contrasted with the cold seeping from the bricks. The source of the light didn't move, but I began to wonder if that shambling figure wasn't using the light to climb back down the ladder and explore the recesses, searching for the source of her unease.

Blackbird had said that just a touch of the spreading rot would be enough. How would we see it spreading over the walls and roof in the shadows? Was it running across the bricks, even now? I sniffed the air, trying to detect the sharp, fetid odour that accompanied the darkspore. Against the background smell of the sewer, it was well masked. The prospect of the dark flows beneath us were more appealing by the second.

Finally I could stand it no more and I leaned out again to peek around the pillar. The two figures were still on the gantry. Then Raffmir stood and stretched, and the other figure pushed back from the rail and ambled past him, the walk not quite human, as if having a jointed limbed body was awkward and unfamiliar.

I watched as the light faded under the arched ceiling.

Perhaps, finally, they had given up and gone.

"I think they've left."

"Are you sure?"

"I don't know. The stone's still pulsing."

"What stone?"

"The one Megan gave me. It's around my neck."

Blackbird pulled her hand from mine and the stone flared with heat and then slowly cooled.

"It's not the wraithkin that's doing that, it's me."

I looked down at her, still tucked into the corner in front of me,

"I don't understand."

She lifted her chin and there was something in her eyes, even in the darkness. It was a faint inner glow, like a green ember dying with a core of inner heat. Her eyes held something I didn't recognise, defiance maybe. "What?" I asked her.

"We need to go, while we have the chance."

She was avoiding my question. What did it mean when the stone reacted like that? Next time I saw Megan, I would ask her. I leaned out again, searching for any sign of them. "I think they've really gone this time. "

"Can you feel her?"

I listened to the inner sense. "I think she's gone. Come on, we'll go downstream."

"We have to get over to the other side. The exit is over there and there are no crossings further down. "

"I am not going up on that gantry."

"I thought you said they'd gone? "

"Yes, but for how long?"

"Fine, then you'll have to jump across like me. It's not that hard."

"I can't get any nearer to the anvil. Can't you feel it? It's like sitting under a thunder cloud."

"You tell me then." Exasperation rang in her tone. "How are you going to get to the other ledge? "

"Perhaps I could climb across the weir, further down?"

"Perhaps you could fall in the water and demonstrate your swimming skills?"

I looked again at where the anvil sat humming in the dark. It had the same quality as the gates at Australia House, only much, much worse. There was a brooding malevolence about it and I knew if I went near it, spite would leap across the air and strike me down. I would not be able to cross via the island, even if I could make the leap. "I'll cross at the gantry. Meet me on the other side. "

"Before we go, we should take a quick look at the door in the wall."

I hesitated, but it was what we had come for. "Can I use your torch?"

"I'll shine it for you, b.u.t.terfingers." I could hear the smile in her voice in the darkness.

We edged back along the ledge to where the dark rectangle showed in the brickwork. It was like an iron safe, set into the wall. The frame had rusted where the damp of the brickwork had leached at it, but the door itself was solid black iron. There was a small square keyhole in the centre.

"It looks pretty solid, doesn't it?" I commented to Blackbird.

"She said it was sealed and that the seals were intact. I wonder what she meant?"

The door was a mere echo of the malevolence of the anvil. Nevertheless, I didn't fancy touching it. "What do you think is inside?"

"Whatever it is, no Fey was meant to reach it."

There was no handle and no other hole I could see. If the square hole were a keyhole, I couldn't see how it turned.

"We should go," I insisted, "before they change their minds and come back for another look.

"I agree. Go and check the gantry is clear. I'll wait for you here and then jump across."

"Why can't you check the gantry?"

"You're the one who insists on using it. I prefer to use the island."

I looked towards the island and then the gantry, both obscure in the dark.

"Can I borrow your torch?"

"What, and lose the only light we have between us? I think it would be better if I looked after it, don't you? "