Gabriel shook her head. "No. But you were right about getting clear. That explosion is a brute. I hope I can make it."

She was a state. Loose folds of flab were caked in thick sable mud, her hair was a tangle of ossifying dreadlocks. Every breath was asthmatic, a battle against coagulating catarrh. She twitched like a palsy victim.

"No problem," he said, wishing to God he meant it.

They waded into the first slough channel.

The fifth island they came to was much larger than the previous four. Iron girders were sticking out among the sedges. There was more grass than reeds on the crest. Soil had begun to accumulate in the crevices between the fragments of stone and cement. Greg cut his calf on something jagged. Cursed.

The island's far shore brought them to within thirty metres of the houses. One more immersion and back on to solid ground. This time it was a long straight ridge parallel to the row of houses. It was cluttered with twisted, drooping chimney stacks, and buckled rafter apexes gnarled with scabby lichens; slate tiles formed a loose flaky shingle beneath their feet, making the going hard.

Just as he reached the summit, Greg heard the sound. A low-volume hum in the background. But rising in pitch and intensity, in menace. A note he was irksomely familiar with.

"Move out, double-time," he said. "The bastards have inflated the hovercraft."

"No more," Gabriel said wretchedly.

"One last time. That's all. Then it'll all be over."

"Yes. Yes, you're right. Only a few minutes left. It's clearing, Greg. So much clearer now."

Realisation struck. He could sense her mind. A pale disconsolate mist of disjointed thoughts, fluttering aimlessly, corrupted with coarse threads of harrowing pain. Gabriel was animated by adrenalin alone, and her endocrine glands were virtually exhausted.

They'd escaped the twins' nullifying effect. Greg let his gland run riot, charging his cerebellum to overload, and screw the risk. Synapses vibrated shrilly under the stress, delusional ripping sounds filtered into his ears, coming from inside his skull, neurone membranes splitting open. His espersense swept out. It was a heady boost. Whole once more.

Two hovercraft were curving away from the tower, each containing three minds, radiant hard-wound balls of mercurial malevolence. Greg recognised Toby riding in one of them, along with a couple of crewmen he couldn't place. Mark and Kendric were paired in the second, along with its pilot. There was no sign of the other minds Greg knew to be out there—Armstrong and Turner, not even Hermione. The tower was an empty shell to his espersense, which meant at least one twin had remained behind. The big question was whether the third hovercraft had been inflated.