Julia was rising from the settee, knuckles screwing sleep out of her eyes. She was wearing a V-necked lilac dress with a pleated skin. A tangerine woollen cobweb shawl was drawn around her shoulders.

She allowed herself a rueful grin. "Midnight, he says. It's gone three."

Then Victor Tyo and one of his squad members carried Katerina in between them. She'd begun to hum tunelessly.

Julia stared at her old schoolfriend, humour and toughness leaching from her face. Whatever zombie incarnation she'd been girding herself for, it wasn't a match for the mental-husk reality provided.

Katerina was lowered on to the settee, utterly uninterested in her environment.

Julia sent Greg a silent desperate plea that this was some awful nightmare, not real.

Walshaw frowned disapprovingly at the grubby rope wrapped round Katerina's wrists. Greg pointed to the fresh scratches on his face.

"See if you can find some padded cuffs," Walshaw told Victor. "And tell Dr. Taylor to stand by. She'll probably need sedating."

Victor nodded crisply and departed, happy to be out of the office.

Julia sank down on to the settee, peering timidly at the beautiful empty shell slumped quiescently beside her. "Kats? Kats, it's me, Julia. Julie. Can you hear me, Kats? Please, Kats. Please."

Katerina's lost eyes swam round. "Julie," she sighed inanely. "Julie. Never thought it would be you. They bring so many others for me, but never you. It's late, isn't it? I can feel it. It's always late when they come for me. We'll be good, won't we, Julie? You and I, when he watches? If we're good then I can go to him afterwards."

"Yah," Julia stammered. Her eyes had begun to brim with tears. "Yah, Kats, we'll be good. The best. Promise." She pulled her shawl off and tucked it clumsily around her friend's trembling shoulders. "I'd like you to leave us alone now," she said without looking round.

Greg had known some officers who could speak like that. Commanding instant obedience. Rank had nothing to do with it, their voice plugged directly into the nervous system.

As he left the office he saw Julia tenderly smoothing back Katerina's dishevelled tresses.

The corridor was narrow with a high ceiling, built from composite panels which cut up the original open-plan floor into a compartmented maze. A pink-tinged biolum strip ran overhead, its unremitting luminescence showing up the threadbare rut running down the centre of the chestnut carpet squares.

Walshaw closed the door behind him. Rachel moved down towards the lift, giving them a degree of privacy.

"I've been doing some checking this afternoon," Walshaw said. "There's a clinic on Granada which claims it can cure phyltre addiction."

"Successfully?" Greg asked.

"Forty per cent of the patients recover. I was wondering. Miss Thompson, isn't it?"