‘I might go to Berwick all the same,’ Perez said, ‘just to find out more about her. Anna wasn’t in Stonebridge for long, and I don’t feel that anyone here really knew her.’

Except Tom King, he thought, and Sarah doesn’t want me talking to him.

He ended his call to Anderson, and on impulse phoned his ex-wife, Sarah. She answered softly, almost in a whisper. ‘Yes?’

‘I need to talk to you,’ he said.

‘You can’t come here because Tom’s home.’ She spoke normally now. She must have moved to a different room where she could talk in private.

‘Can you come to me? I’m staying in the hotel.’

‘I don’t know,’ she said. ‘If we meet in the bar, someone might see us. This place is nothing but gossip.’

‘I’m starting to realise that,’ Perez said. He gave her his room number, and it occurred to him that anyone listening in would assume they were having an affair. It was easy to jump to the wrong conclusions, and perhaps that was what everyone involved in this case was doing.

Half an hour later Sarah tapped on the door and he let her in. There were melting snowflakes in her hair and she was shivering, though the hotel room was very warm. He made her tea, struggling to open the tiny plastic pot of UHT milk, and gave her his chair. The only place for him to sit was the bed, so he perched there.

‘Why didn’t you tell me you tried to get rid of Anna from the school, even though you were in favour of her getting the job at the start?’

Sarah blushed but she didn’t speak.

‘I can’t help you if you don’t talk to me,’ Perez said.

‘It was a mistake to give her the post,’ Sarah said at last. ‘She was too young and too inexperienced. She let the children get away with murder.’ She realised what she’d said and blushed again.

‘Did Tom know Anna before she moved here?’ Perez felt so frustrated that he wanted to shake the truth out of Sarah. He wondered how he could have loved her so deeply, how he could have spent all those nights dreaming about her after she’d left him.

I felt sorry for her, he thought. Because she was desperate for a child and suffered one miscarriage after another. I blamed myself. It wasn’t a good basis for a marriage.

Sarah looked up at Perez over her mug of tea. ‘I thought Tom might already know her. I couldn’t be certain.’

‘What gave you that idea?’

‘I saw them together once in the health centre just after Anna moved here,’ she said. ‘Tom’s car was in for a service, and I’d called in to give him a lift home. Anna was in the waiting area when I got there. She didn’t have an appointment – she wasn’t there because she was ill. I think she was just hanging on until he’d finished work. It looked as if she was hoping to surprise him. Anna didn’t know who I was – she must have thought I was just a patient – and when he appeared she called out to him: “Tom! Look who it is!” It was as if she thought he’d be pleased to see her.’