Clara put her hand to her mouth. ‘Oh my God, that poor kid.’

Rose glanced at her with the smallest flicker of confusion, almost, Clara thought, as if Hannah’s suffering hadn’t occurred to her in all of this. ‘I didn’t find out for many years that Hannah had overheard us, not until I saw Beth again,’ she went on, ‘and by then it was far too late. In the meantime she grew up, becoming more and more disturbed, fixated on what she’d learned. She became obsessed with Oliver and me, with all of us – her “real” family as she thought of us. She knew the hospital Beth used to work in and tracked me down there. After a while she began to skip school, getting the train over here and following Oliver to work, or standing outside the children’s school, becoming more and more resentful.’ She turned to Tom. ‘She saw you kids as having the perfect life, the life that she should be living.’

‘Didn’t you confront her?’ Tom asked angrily. ‘Talk to her?’

‘We didn’t know!’ Rose cried. ‘Even Beth had no idea until years later. Hannah always kept her distance, never approaching us, or letting herself be discovered. We had no clue that she even knew about us! And then, when she was sixteen and Emily had just turned eighteen, she engineered a way for the two of them to meet. They became friends.’

‘And you still had no idea who she was?’ Clara asked.

‘No! She told Emily her name was Becky, and she never came here to the house, not that I’d recognize her if she did. We knew Emily had a new friend but I didn’t make the connection. Why would I? The Jennings lived miles from us in Cambridgeshire, I had no idea Hannah knew about us all, I had no reason to suspect.’

‘So how did you find out?’ Mac asked.

At this Rose began to cry again. ‘One night Hannah told Emily. She told her everything. Who she really was, that Oliver was her father, that she and Emily were half-sisters, that we’d given her away to near strangers to be rid of her.’

‘My God,’ Tom said.

‘But it was worse than that. Hannah knew I’d been the only person present when her mother died, and over the years she had convinced herself that it was I who killed her, that I’d pushed her!’

‘And Emily believed her?’ Tom asked.