Her conversations with Anderson did little to lift her spirits. They had found no identifiable fingerprints in her flat and the upstairs neighbour, who it turned out was named Alison Fournier, a twenty-eight-year-old IT specialist from Leeds, had been traced to her cousin’s home in Middlesex, where she’d been staying since a day before the break-in. They had ‘no reason to think she was involved’, Anderson said.

‘But … what about the sweatshirt?’

‘We’re satisfied that it belongs to Ms Fournier.’

‘Well, what now, then?’ she asked desperately.

‘We’re doing all we can,’ he replied. ‘Clara, we are looking into everything, I assure you we’re doing our utmost to get to the bottom of this, and I’ll be in touch as soon as we have more news.’

‘Yes,’ she said quietly, ‘OK.’

After she’d put the phone down, she met Mac’s gaze and he shook his head in silent sympathy.

‘This is day eight,’ she told him helplessly. ‘Day fucking eight since Luke went missing. Four days since they found the van. They’ve had no useful response to the appeal, he’s just completely vanished. How can that be possible? How can anyone disappear into thin air?’ Her voice rose in despair. ‘What if this is it, Mac? What if they simply give up on him and we never see Luke again? If his mum and dad never see him again?’

‘No one’s going to give up on him, Clara,’ Mac told her firmly. ‘They know what they’re doing. We have to trust that they’ll find him.’

‘I feel so fucking useless.’

They sat listening to the rush-hour traffic passing below, the noises from the kebab shop on the street directly beneath them. Through the wall came the applause and canned laughter of the neighbour’s TV set. Day was drifting into night, but neither of them moved to turn on the light and a thick gloom settled into the corners of the room.

‘Whoever sent the emails knows Luke well,’ Clara said. ‘Someone he must have been close to once, who for whatever reason holds a grudge.’

Mac frowned. ‘Yes, but surely the police have looked into who that might be?’

She nodded impatiently. ‘Yeah, maybe, but they said they’d not found anything suspicious.’

‘So …?’

‘Well, I don’t know – maybe we should start looking into it ourselves? Between us we’ve probably got a good idea of the different girlfriends, colleagues, flatmates and so on Luke has had over the years. Maybe the police have missed something?’

‘Hmmm …’ said Mac doubtfully.