The screen went blank. Black Star had gone, and as Elena sat back in her chair, her hands were trembling.

Deveraux picked up her 'secure speech' Xda mobile, tapped the screen and put the device to her ear. She glared at Elena. 'You should have kept him online. The longer we have contact, the more chance there is of locating him.'

'We don't even know Black Star is a he,' said Danny, springing to the defence of his friend. 'And it's not Elena's fault if you can't find the target.'

'It's a man, I know it's a man,' said Deveraux over the ring tone in her ear.

Her call was answered. 'No good,' said a voice without waiting for the question. 'He's spoofed his ID through the Philippines and Berlin. We'll never find him like this.'

Deveraux hung up, turned to Fergus Watts and shook her head.

They were getting nowhere. In the four weeks since Elena had been making regular contact, Black Star, or the 'target', as the shadowy Internet figure was now termed, had never once disclosed a single personal detail: gender, age, location. Nothing.

Fergus was sitting in a wheelchair. He still wasn't used to it; it was almost as bad as being cooped up in a prison cell. Around his neck dangled the earpiece lead of a mini iPod. He had surprised Danny when he'd bought it three weeks earlier, saying it would give him something to do during any down time they had. He'd chosen the smallest and cheapest model, an iPod Shuffle, and it had accompanied him everywhere since Danny had shown him how to load it with the old rock music he liked.

He looked over at his grandson. 'Why don't you and Elena go outside for a while? Get some air. You've both been stuck in here for too long.'

The two teenagers needed no second invitation; they too had begun to feel like prisoners.