‘What is it now, Reg?’

‘Why did you prescribe paracetamol for Mrs Wrangton?’

‘Because I thought it suitable for her, of course. She was allergic to aspirin.’

Wexford looked despairingly at his friend. ‘Now he tells me. I’d rather gathered it. I mean, today I caught on, but you might have told me.’

‘For God’s sake! You knew. You said to me, Nurse Radcliffe told me all about it. Those were your words. You said . . .’

‘I thought it was asthma.’

Crocker sat on the edge of his desk. ‘Look, Reg, we’ve both been barking up the wrong trees. There was asthma in Mrs Wrangton’s family. Mrs Betts has nettle rash, her brother was a chronic asthmatic. People with asthma or a family history of asthma are sometimes allergic to acetylsalicylic acid or aspirin. In fact, about ten per cent of such people are thought to have the allergy. One of the reactions of the hypersensitive person to aspirin is an asthmatic attack. That’s what Mrs Wrangton had when she was in her forties, that and haematemesis. Which means,’ he added kindly for the layman, ‘bringing up blood from an internal haemorrhage.’

‘OK, I’m not bone ignorant,’ Wexford snapped, ‘and I’ve been reading up hypersensitivity to acetylsalicylic acid . . .’

‘Mrs Wrangton couldn’t have had aspirin poisoning,’ said the doctor quickly. ‘There were never any aspirins in the house. Mrs Betts was strict about that.’

They were interrupted by the arrival of smiling Dr Moss. Wexford wheeled round on him.

‘What would you expect to be the result of – let me see – one point two grammes of acetylsalicylic acid on a woman of ninety-two who was hypersensitive to the drug?’

Moss looked at him warily. ‘I take it this is academic?’ Wexford didn’t answer. ‘Well, it’d depend on the degree of hypersensitivity. Nausea, maybe, diarrhoea, dizziness, tinnitus – that’s ringing in the ears – breathing difficulties, gastric haemorrhages, oedema of gastric mucosa, possible rupture of the oesophagus. In a person of that age, consequent upon such a shock and localized haemorrhages, I suppose a brain haemorrhage . . .’ He stopped, realizing what he had said.

‘Thanks very much,’ said Wexford. ‘I think you’ve more or less described what happened to Mrs Wrangton on June 2nd after she’d taken four three hundred milligram tablets of aspirin.’

Dr Moss was looking stunned. He looked as if he would never smile again. Wexford passed an envelope to Crocker.

‘Those are aspirins?’

Crocker looked at them, touched one to his tongue. ‘I suppose so, but . . .’

‘I’ve sent the rest away to be analysed. To be certain. There were fifty-six in the bottle.’

‘Reg, it’s unthinkable there could have been a mistake on the part of the pharmacist, but just supposing by a one in a million chance there was, she couldn’t have taken forty-four tablets of aspirin. Not even over the months she couldn’t.’

‘You’re being a bit slow,’ said Wexford. ‘You prescribed one hundred paracetamol, and one hundred paracetamol were put into that bottle at Fraser’s, the chemist’s. Between the time the prescription was made up and the day before, or a few days before, or a week before, she died, she took forty tablets of paracetamol, leaving sixty in the bottle. But on June 2nd she took four tablets of aspirin. Or, to put it bluntly, some time before June 2nd someone removed those sixty tablets of paracetamol and substituted sixty tablets of aspirin.’