Charlie opened her bag, pulled out the exhibition catalogue Jan Garner had given her and put it in front of him, wondering if he was in a fit state to pay attention. She could have boasted that, unlike him, she’d made real progress, but she’d have felt too cruel and, besides, it was about to become obvious.

‘The Murder of Mary Trelease,’ Simon read aloud. ‘Oil and watercolour. £2,000.’

Charlie passed him the sales list. ‘That’s two thousand quid eight years ago, don’t forget. J. E. J. Abberton mustn’t be short of a bob or two. Only one problem: his address, as listed there, doesn’t exist.’

‘Are you sure?’

She tried not to take the question as an insult. ‘I spent what felt like hours on the phone to 118118, checking and double-checking. There were eighteen paintings in Aidan Seed’s exhibition. Three were sold to real people with real addresses: Cecily Wyers, Saul Hansard and Kerry Gatti.’

‘You reckon Cecily Wyers is Martha’s mother?’

‘Seems likely, based on what Jan Garner said about a mother and daughter fighting over whether to buy a picture.’

Simon nodded his agreement.

‘Cecily, Gatti and Hansard bought one picture each, leaving fifteen. Those were sold to our old friends, the gang of nine.’ She read the names aloud, out of the alphabetical order she was used to. ‘Mrs E. Heathcote, Dr Edward Winduss, Mr P. L. Rodwell, Sylvia and Maurice Blandford, Mrs C. A. Goundry, Ruth Margerison, Mr J. E. J. Abberton, E. & F. Darville, Professor Rodney Elstow. The Darvilles bought four pictures, Rodney Elstow three and Dr Edward Winduss two. The others bought one each.’ Charlie paused to take a quick breath. ‘The addresses Jan’s written down for these nine buyers don’t exist. Or rather, eight of them don’t exist at all, and one—’

‘They’re not ex-directory?’

‘Nope.’

‘I don’t suppose it’s possible none of the nine has a telephone, ’ said Simon.

‘How likely is that? Anyway, no. I rang the post office once I’d finished with directory enquiries. They don’t exist, Simon. Apart from Ruth Margerison’s.’

Simon looked down at the list. ‘Garstead Cottage, The Avenue, Wrecclesham . . .’

‘Villiers is in Wrecclesham, the boarding school Wyers and Trelease went to. While I was on to the post office, I asked for the school’s postcode and full address, and guess what also turned up under the “Villiers” listing? Ruth Margerison’s address and postcode.’

Simon frowned. ‘I don’t follow.’

‘Villiers’ grounds are so vast, they cover several postcodes. There are about twenty school buildings in total, all listed individually. One of them’s Garstead Cottage. It’s even on The Avenue, which must be the name of a road within the grounds. I rang Villiers, asked to be put through to Ruth Margerison at Garstead Cottage, and was told nobody by that name lived there.’

‘Did you ask who did?’