Dr Moss found his voice. ‘That would be murder.’

‘Well . . .’ Wexford spoke hesitantly. ‘The hypersensitivity might not have resulted in a stroke. The intent may only have been to cause illness of a more or less severe kind. Ulceration of the stomach, say. That would have meant hospitalization for Mrs Wrangton. On the Welfare State. No exorbitant nursing home fees to be paid there, no swallowing up of capital or selling of property. Later on, if she survived, she would probably have been transferred, again for free, to a geriatric ward in the same hospital. It’s well-known that no private nursing home will take the chronically sick.’

‘You think Mrs Betts . . .?’ Dr Moss began.

‘No, I don’t. For two good reasons, Mrs Betts is the one person who wouldn’t have done it this way. If she had wanted to kill her mother or to make her seriously ill, why go to all the trouble of changing over sixty tablets in a bottle, when she had only to give Mrs Wrangton the aspirins in her hand? And if she had changed them, wouldn’t she, immediately her mother was dead, have changed them back again?’

‘Then who was it?’

‘I shall know tomorrow,’ said Wexford.

Crocker came to him at his office in the police station.

‘Sorry I’m late. I just lost a patient.’

Wexford made sympathetic noises. Having walked round the room, eyed the two available chairs, the doctor settled for the edge of Wexford’s desk.

‘Yesterday,’ Wexford began, ‘I had a talk with Mrs Elsie Parrish.’ He checked the doctor’s exclamation and sudden start forward. ‘Wait a minute, Len. She dropped a matchbook before we parted. It was one of those with a glossy surface that very easily take prints. I had the prints on it and those on the paracetamol bottle compared. There were Mrs Betts’s prints on the bottle, and a set that were presumably Mrs Wrangton’s, and a man’s that were presumably the painter’s. And there was also a very clear set identical to those on the matchbook.

‘It was Elsie Parrish who changed those tablets, Len. She did it because she knew that Mrs Wrangton fully intended to retire to Summerland and that the first money to go, perhaps before the house was sold, would be the few thousands of capital she and Doreen Betts were to share. Elsie Parrish had waited for years for that money, she wanted to buy a car. A few more years and if she herself survived it would be too late for driving cars. Besides, by then her legacy would have been swallowed up in nursing home fees.’

‘A nice old creature like that?’ Crocker said. ‘That’s no proof, her prints on the bottle. She’ll have fetched that bottle often enough for old Ivy.’

‘No. She told me she had never been upstairs in Ivy Wrangton’s house.’

‘Oh, God.’

‘I don’t suppose she saw it as murder. It wouldn’t seem like murder, or manslaughter, or grievous bodily harm, changing tablets over in a bottle.’ Wexford sat down, wrinkled up his face. He said crossly, dispiritedly, ‘I don’t know what to do, Len. We’ve no way of proving Mrs Wrangton died of aspirin poisoning. We can’t exhume her, we can’t analyse “two handfuls of white dust shut in an urn of brass”. And even if we could, would we be so inhumane as to have a woman of – how old is Elsie Parrish?’