She swallows, playing with the rings on her hands. She has two on her wedding finger and a signet ring that I recognize on the little finger of her right hand. Heather and Flora used to wear them too. Family rings, Heather called them. ‘I didn’t think she knew them. And it might be a coincidence. But Deirdre stayed here in one of the caravans. About five weeks ago. I saw it written in the register …’ she glances up at me, pain etched on her face ‘… in Heather’s handwriting.’

So Heather had met Deirdre Wilson. What happened between them? Did she do or say something to make Heather kill her?

‘But she’d never mentioned her to you?’

‘Never,’ she says firmly. Margot uncrosses her legs and reaches for her tea.

I wait for her to settle back into her chair before asking, ‘Can you explain what Heather was like as a child? I know I became friends with her when we were twelve, but before that, when you lived in Kent.’

Margot looks wistful, her gaze going to the French windows as though a child version of Heather is out there, playing on the lawn. ‘She was sensitive. A born worrier. My mother, when she was alive, said that Heather lived close to the well. She cried easily.’

I don’t remember ever seeing Heather cry. Even after Flora went missing. But I keep quiet.

Margot chews her lip thoughtfully. ‘Flora was more fanciful, I suppose. Heather … Well, Heather was practical. She looked after Flora, even though she was the youngest. And she was always so self-contained, even as a child, content in her own company, sketching or writing or playing alone with her stuffed animals. But she loved being with Flora too. They didn’t seem to need anyone else.’ She sighs. ‘I shouldn’t be talking about her in the past tense. Heather’s still here, still with us.’

I remember how honoured I’d felt when I was finally accepted into their little group. How Heather had cared for me when I was ill once with a tummy bug, holding my hair back as I was sick and looking after me until my mum got home from work.

‘The waters run deep with Heather,’ she says. ‘You never really knew what she was thinking. She never wanted to be any trouble. After Ethan was born she suffered post-natal depression but she didn’t tell anyone for ages that she was feeling so awful. It was only when she couldn’t hide it any more that she admitted it. She didn’t want to make a fuss.’ She closes her eyes as if the memory is too painful, and my heart hurts for her.

When she looks up there is a different expression on her face, as though she’s contemplating telling me something she isn’t sure she should.