Emma stopped wailing. I unlocked the door and slipped into the room, clutching the key tightly in my sweaty palm, so tightly it made my hand throb.

She sat on the little white bed hugging her knees to her chest. Her eyes were red and swollen from crying. Snot ran from her nose onto her lips. I looked around the room, not surprised to find it similar to mine, though more colourful as the walls had been painted with pale grey bunnies and enormous red and orange flowers. The bed was covered with a frilly pink duvet. A white bear-shaped rug lay on the wooden floorboards. From the windows hung frilly lilac curtains which had been nailed around the edges into the wall. The middle of the curtains had been sewn together to prevent even the slightest shard of light from penetrating the room. A cute miniature tea set sat on a little white desk alongside a large sandy-coloured teddy bear who wore a scarlet bow around his fluffy neck. Mother had clearly made an effort for her new doll.

‘Hi,’ I said, perching on the edge of the bed.

She stared at me with her big blue eyes and sniffed. ‘My head hurts.’

‘Does it? Oh, well, maybe if we go downstairs I can find something to make it feel better.’

‘I’m not allowed,’ she whispered, her eyes darting towards the door, ‘M-M-Mother will be cross if, if, if I go out.’

‘No she won’t. She sent me up here to see if you were OK, but there’s something important I have to tell you first. A secret.’

Emma sat up at this. I noticed she wore one of my old nightgowns. A long white one embroidered with daisies. A strange twinge pulled at my chest. She was my replacement. It was as clear as glass.

I leaned forward and stroked hair out of her eyes.

‘What secret?’ she said.

‘If I tell you, you have to promise me not to say anything. Promise?’

She hesitated, looked at the door again. After a few seconds she whispered, ‘I promise.’

‘OK,’ I paused, trying to think of the best way to explain, ‘the woman who is looking after us isn’t well. There’s something wrong with her. She took me from my real parents when I was about your age and told me I was her daughter. She told me my name was Mirabelle, but my real name is Polly. And now she’s doing the same thing to you.’

‘I don’t understand,’ Emma said, wiping her nose with the back of her wrist.

‘What’s your name? Your real name?’

The girl frowned, as if concentrating really hard. She hadn’t been here for very long. There was no way she could have forgotten her real name already, but Mother was clever. She skewed the truth, made you think the way she thought.

‘My old name is Emma,’ she whispered.