This patient was not even a woman. After spending a short time with him, it was one of the few clinical observations Raven would have trusted Dr Fowler to get right.

Raven stood with his arms folded and tried to think. Something was amiss, but he was struggling to identify what that something might be.

The patient’s name was George Porteous. He was a young man with pale skin and a full head of red hair. He was lean but not thin, someone who had been well nourished. He looked to be in good health apart from the fact that he was soporous and could not be roused.

‘He has been like this for two days,’ Dr Fowler said. ‘But at least the twitching has stopped.’

‘The twitching?’

‘Yes. Of the facial muscles. He was delirious for a while, muttering and clutching at the bed clothes.’

‘You mean convulsions?’

‘No, I would not say convulsions.’

‘Any fever?’

‘No fever. The pulse was elevated initially but not now.’

Raven approached the bed and laid a hand on the patient’s forehead. It was warm, not hot, and free from perspiration. He gently lifted each eyelid in turn and found both pupils were normal in size. The patient’s breathing was shallow, so shallow that Raven had to put his ear to the patient’s chest to confirm that it had not ceased altogether.

‘Is he a drinker?’ Raven asked, although he thought it an unlikely explanation as there was no smell of alcohol.

‘Not according to his sister.’

‘Did he complain of any other symptoms? Headache, giddiness or palsy?’

‘No. As far as I am aware, he experienced no unusual symptoms except for fatigue. He took to his bed and was then found by his sister to be at first delirious and then as you see him now.’

Raven had to admit to himself that he was mystified.

‘I applied leeches,’ Dr Fowler said, ‘but rather curiously they all fell off and died. I did manage to bleed the patient, though,’ he added, indicating a bleeding bowl on the floor next to the bed. ‘Several ounces, but to no avail. My next suggestion was going to be a clyster to purge the bowels.’

Raven might have been at odds with Simpson on certain matters, but he was wholeheartedly in agreement about the limited usefulness of bleeding and purging.

‘I think perhaps he has been drained of enough,’ he said.

They opted to continue their discussion out of earshot of the patient, though he did not appear likely to hear much in his current state. Raven followed Dr Fowler into the hallway, a dark passage lit only by a small window into which little light was admitted due to the height of the buildings opposite.

‘It is most perplexing,’ Dr Fowler said. ‘A young man, previously in good health. Clean living. Recently bereaved, poor soul.’

‘Bereaved?’