Out in the corridor, I waited, silently and almost holding my breath. The Doctor had told me I mustn’t make a sound. It was imperative that Mama not know I was close by. So I listened, my heart thumping in my breast, to the conversation in the next room.

‘You’ve forced me to advance the Great Work somewhat, Doctor,’ Mama said. ‘But my colossal scheme remains as it was. My rocket will explode high in the atmosphere, raining down Mr Sweet’s beneficence onto all Humanity.’

‘And wiping us all out!’ This was the Doctor’s friend. ‘You can’t!’

Then there was a long silence. I heard little except the chitter-chatter of Mama’s machines and the soft, horrid gurgling which I knew to be Mr Sweet.

Mama spoke again. ‘For some little time I worked with an organisation. We plotted and schemed our little schemes bringing delightful chaos to this world. But my ambition soon outgrew C.A.B.A.L. – what use have I for such pygmy notions? My ambitions are on a scale unprecedented by any human being! My new Adam and Eves will sleep for but a few months before stepping out into a golden dawn. Is it not beautiful, Doctor?’

But the Doctor did not reply. Something about his silence seemed to discomfit Mama. She cleared her throat in a way I found familiar from those (very rare occasions) on which she felt a trifle uncertain.

Then it came. And my heart felt as though it had leapt into my mouth. ‘Tell us about Ada, Mrs Gillyflower.’

‘What?’ Mama sounded thrown.

‘Your daughter,’ the Doctor persisted. ‘Tell us about your daughter.’

Mama gave a laugh, a cheerless, ghastly laugh that chilled my blood. ‘Ada? How can you speak of such trivia when my hour is at hand? The child is of no consequence.’

No consequence! The words cut me like a blade. All the years I had given to her. My very best years …

‘Is that why you experimented on her?’

I almost gasped – and clapped my hand over my mouth. I must not give myself away! But what devilry was this? Experimented?

‘I had a long time to study Ada’s face while she was caring for me,’ said the Doctor and his voice rang with authority. ‘You know why she’s blind? Why she’s actually blind?’

My mind raced. I could feel all my certainties, everything I had known and believed all my life tumble and shiver like sand through a glass.

‘Yes!’ yelled Mama. ‘Because my disgusting sot of a husband came at her with an explosive mixture! The drink had turned his wits—’

‘No. The signs are all there,’ continued the Doctor remorselessly. ‘The pattern of scarring. Chemical burns. But systematic. You used her as a guinea pig, didn’t you?’

‘Oh God,’ said the Doctor’s friend.