What things we say, what promises we make, when we are pleading for our lives. But the way Dr McTavish stared at me, open-mouthed with horror, told me I was right. And that Mrs Rose had been right in her suspicions.

‘Sir,’ I said, ‘here is the thing. I do very much fear that if you don’t help me survive the gallows, then I might scream your secret to the world, and those would be my last words, for all of Edinburgh town to hear.’

‘No one will pay any attention to the last pathetic words of a baby-killer,’ Dr McTavish spat.

‘You will loosen my hands,’ I said, ignoring him, ‘for they’ll be bound at my chest, not behind my back – you will make sure of that. You will help me slip them up, under the noose. And you will make sure that the noose is not going to strangle me or break my neck. And if you do not do that, but put that noose tight and firm around my neck, I will scream on that gallows and tell everyone you are a poisoner and that if they dig up your wife’s grave and examine her, the body will be full of laudanum.’

I knew about post-mortems by then, you see. I knew surgeons could make the dead talk, just as they had weighed my poor babe’s lungs and seen that she had taken breaths.

‘The folk of Edinburgh will listen with great intent to what I say on the gallows,’ I went on. ‘And the broadside-writers will be there, and everything will be scribed and put into news chronicles and books. If I tell them the hangman’s wife lies in a Kelso kirkyard full of his poison, it will be an almighty scandal.’

A rodent scratched at the floor and we both glanced at it, but only for a moment, for me and Dr McTavish were coiled to each other now.

‘Mistress Dickson,’ he replied, ‘I wonder if we might both do each other a favour. You remember Mrs Rose well. You know what she looks like, and you were clearly a confidante of hers.’ I nodded. ‘Well, as it happens, I have glimpsed her, here in this very town.’

‘Have you indeed, sir?’ I said, keeping calm and still. ‘How very interesting for us both.’ Here? In Edinburgh? That wench has been here all along?

‘She is whoring again,’ he whispered. ‘Any gent will do, it seems, apart from me, who she refuses to see. I have tried, a number of times, but she will not conduct business with me. And I do have a particular hankering for her. A craving, if you understand me.’

We stood a moment – hangman and condemned – and considered the situation.