There were many side tracks, most of them half-hidden, for where human foot no longer trod, a small army of shade-loving plants had made itself at home beneath the shelter of ancient oak, venerable ash and guardian holly. The place must be rich with healing herbs and fungi. I longed to explore those byways, to forage and to learn. The forest called me. But no voice was louder than the monster’s. My own inner voice suggested I might slip out again later, on my own. If I kept my ears blocked I should not be led astray. And who could object to a wise woman gathering herbs?

The stands of oak and ash gave way to willow, elder and alder. Sunshine streamed down between the leaves, brightening the path. Although the monster’s voice was loud, I could also hear running water.

“This river,” said Grim. “Deep, is it? How do we get across?”

“We wade,” said Onchú. “At this time of year the water is relatively shallow. There’s a boat, but it fell out of use long ago. We should block our ears now. If you need to draw my attention or Donncha’s, make a gesture or tap us on the shoulder. Your earplugs won’t keep out the monster’s voice entirely, but they’ll mute it so it’s bearable.”

I could imagine what kind of response there’d be to the sudden hand on the shoulder, when a man could hear nothing and was traversing an island that held some kind of unspeakable creature. I knew enough about fighting men to be fairly sure the first reaction wouldn’t be a polite query as to whether anything was wrong.

“Stay well away from the thorns. And keep in sight of us at all times. We won’t be on the island for long.”

“All right?” asked Grim as we took our supplies of woolen wadding from our pouches.

“Fine.” I was sorely tempted to disobey Onchú’s instructions; how could we investigate properly if we couldn’t hear? But I’d given Geiléis my word, so I blocked my ears. I saw on Grim’s face, as he stuffed the wadding in his own ears, that his thoughts were running on the same path. If the tower had nothing to tell us this morning, we might need to come back another time. An unofficial visit, without the escort.

Our track through the woods had taken us down a gentle slope; at no point during our walk had the tower been visible. Now, as we came out from the cover of the trees, the ford lay before us, a broad expanse of rippling water, with the track reappearing on the far side, climbing before it vanished into another tract of woodland. To our right, downstream, was the island, and on it stood the Tower of Thorns.

“Morrigan’s curse,” I muttered. If you wanted to keep the most savage of enemies, the most cunning and troublesome of adversaries in custody, this would be the place to do it. The circular tower was higher than I had thought when I’d seen it from a distance; it seemed to reach for the sky. It was all of shaped stones, laid cunningly to create the curved walls. Inside, I assumed, there must be a spiral stair leading to the high chamber from which the monster wailed. From this spot by the ford, I could see neither door nor windows. The tangle of thornbushes wreathing the tower must conceal an entry; how else had the creature got in? If it could fly, it would surely have snatched the opportunity to escape, whether to wreak further havoc in the district or to wing its way to freedom.