And she had nothing. Maggie was either dead, or she had been abducted and was a prisoner somewhere – and it could be anywhere – or she had been trafficked, in which case she could be anywhere in the world, working most likely in the sex trade, watched day and night, with no documents and no money. She’d be given ready access to drugs and alcohol and, when she was no longer of value, she’d be killed and disposed of, dumped in a lake or river, buried in a forest or desert, or thrown into an incinerator. No one would miss her. No one would report her absence to the police, and even if they did, the police wouldn’t be able to do anything. They would have no idea who she was.

Martin Cooper answered on the second ring.

‘Yes,’ he said. ‘DI Wynne?’

She was stung by the hope in his voice.

‘Just a routine call, I’m afraid,’ Wynne said. ‘To let you know we are still pursuing all avenues as thoroughly as we can. And to answer any questions you might have.’

‘I don’t have any.’ His voice was flat. ‘But thank you for checking in.’

‘Not a problem,’ Wynne said. ‘By the way, is your son OK?’

‘More or less,’ Martin Cooper said. ‘Although I’m not sure OK is the best description. He was very drunk.’

‘Perhaps he needed to let off some steam,’ Wynne said. ‘He’s safe, at least.’

‘Exactly,’ Martin Cooper said. ‘And he would have been gone longer but someone found him and brought him home.’

‘That’s fortunate,’ Wynne said. ‘Better than having him stagger around the streets. He was lucky to run into someone so responsible. Not everyone is that civic-minded these days, especially when it comes to teenage boys.’

‘He was a teacher,’ Martin said. ‘So he wasn’t scared of fourteen-year-old boys. It was an odd coincidence, actually. I knew him. He was Sandra’s maths teacher in school. Mr Best.’

Wynne almost missed it. She had not been fully paying attention; she was going out that evening – a rare occurrence – with someone she had met at the gym. Wynne was having a coffee after a spinning class; the woman had been in the class and, afterwards, had sat at her table and pointed at the coffee.

That won’t re-hydrate you, she said.

It might give me some energy, Wynne replied, aware that she was still red-faced and sweating, whereas the woman – Nicky, it turned out – was showered and dressed and fully composed.

Try one of these. She had a bright green antioxidant fruit shake. It’s a great boost.

Wynne shook her head. Coffee, for me, she said.

Want to meet for one? the woman asked. Or a real drink?

And they were meeting tonight.

She paused.

‘Best?’ she said. ‘Late fifties? Balding? Metallic glasses?’

‘Yes,’ Martin said. ‘You know him?’

‘I do.’

‘Did he teach you?’