‘I’ve taken compassionate leave for a few days,’ said Weston. ‘I need to look after Susan. The head of my school has been very understanding.’

Fry became aware of Mrs Weston standing in the background, listening. She was pale and looked tired.

‘Have you found Martin Stafford?’ she asked.

‘Not yet, Mrs Weston,’ said Hitchens.

‘So he’s got away.’

‘We’ll locate him, eventually.’

‘He always had a violent tendency.’

‘We want to eliminate him from the enquiry, obviously.’

Mrs Weston stared at him as if she didn’t understand what he was saying.

‘Susan –’ said her husband.

‘I always said he was no good,’ she said. ‘I was always afraid it would come to this.’

‘I don’t think we know any more about Martin Stafford than we’ve told you already,’ said Mr Weston. ‘There might be something at the house in Totley, I suppose. I mean Jenny’s house. He might have written to her or something.’

‘Trying to creep back,’ said his wife.

‘We’ve already looked there,’ said Hitchens. ‘We found this –’

The Westons examined the photocopy that he showed them. It was a note rather than a letter – just a few lines about an arrangement to meet somewhere. But it was addressed to Jenny, and it was written in terms that suggested a close relationship.

Mrs Weston coloured faintly when she reached the line about fruit flavours. ‘There’s no name on it,’ she said.

‘No,’ said Fry. ‘That’s why we’re showing it to you. In case you recognize it.’

‘You think it might be from Stafford?’ asked Mr Weston. ‘There’s no date on it, either.’

‘Unfortunately not.’

‘I can’t really remember what his writing was like. Susan?’

‘No,’ said Mrs Weston. ‘I mean, I don’t know. It could be.’

‘Did he ever write to you? Might you have something that we could compare it to?’

The couple looked at each other. ‘Have we still got that postcard?’ said Mr Weston.

His wife went to a mahogany dresser and opened a drawer. It was one of those drawers that were always full of things that you never wanted. But Mrs Weston soon located a plastic wallet of the kind that usually contained holiday snaps.

‘I don’t know why we kept it,’ she said. ‘But you can see what sort of man he is.’

Fry studied the postcard. It showed a view on one side of a beach lined with tourist hotels.

‘Hawaii,’ she said. ‘Very nice.’ She turned the card over. It was addressed to the Westons and signed ‘Martin (your former son-in-law)’. The rest of it seemed fairly innocuous – a few lines about how hot the weather was, how luxurious the hotel, how stimulating the nightlife. ‘Spent nearly £2,000 already!’, it said, as if it was a boast.

‘I’m not sure what it tells me,’ said Fry. ‘This holiday was presumably after the divorce.’