McLevy appeared unperturbed. ‘That’s as may be, but when I spoke to him earlier, Mr Jarvis himself corroborated certain details of Mr Quinton’s testimony.’

‘Indeed, and Jarvis told me all of this the moment I returned from Dunblane. However, Mr Jarvis and Dr Raven both withheld some important details in order to protect Dr Banks’s honour. Dr Raven did so even when to reveal this might have assisted him in his plight. Bear that in mind when weighing his character and the credibility of his word against that of an employee who has been robbing me from under my own roof.’

Mr Findlay looked intrigued, McLevy wary, as though biding his time before he might pounce once again.

‘Do elaborate,’ said Findlay.

‘Archie Banks was gravely ill. He had been suffering from carcinoma of the tongue and, as a medical man, he knew he was facing a painful and imminent death. Dr Raven suspected that Archie took his own life, to spare himself the worst. Dr Raven kept this conclusion from Mr McLevy for the same reason that he instructed Jarvis to dispose of the evidence of how Archie died: because he did not wish it to become a matter of public knowledge. He was concerned for the effect it would have on Dr Banks’s widow, Sarah.’

Raven could have wept at the mention of her name from the lips of someone else who cared about her.

‘To be clear,’ said Findlay, ‘you are saying you would concur with Dr Raven’s conclusion that Dr Banks took his own life?’

Simpson paused a moment. The room fell perfectly still.

‘No,’ he said.

Raven gaped.

‘Then who did kill him?’ Findlay asked.

‘I will show you. How is your circulation, Mr Findlay? Are your hands nice and warm?’

Findlay looked like he didn’t understand the question, and certainly could be forgiven for not understanding the relevance of it, for neither did Raven.

Simpson signalled to Jarvis, who handed him his bag.

‘This is a stock bottle of chloroform, filled to capacity, as was the one taken by Dr Banks from my store cupboard two nights ago. I know this for a documented fact, just as Mr Quinton knew it, because he wrote it down in his ledger. Hold it for me, please.’

Simpson placed the bottle in the palm of Findlay’s hand, fixing his fingers around it.