‘Later that evening, when I asked Beth about her afternoon, and she told me she’d gone to the park with Lisa and some of the others from school, I didn’t think to pick her up on it. To ask her had she not been to Melissa’s? Teenagers can be secretive. Reluctant to share details of their lives, especially with parents. I suppose I was still happy to think that Beth had someone she could talk to. Someone to support her. So, I let it go.’

The next day – Saturday – Mark had taken both girls to the Tennis Club, and I had spent some time online, looking at flights, browsing through various websites for accommodation in Rome.

‘I compiled a few different pages, but when I went to print them, I found the printer was jammed. A page was stuck, and once I’d freed it and reset things, the printer resumed, working its way through the print queue.’

It was when I took the sheaf of printed pages off the printer and started leafing through them that I found the letter.

‘What letter?’ Mark asks, his forehead creased with concentration.

‘It read like a suicide note,’ I say carefully, watchful now while he takes this in.

To whoever finds this … I have struggled for some time … This disease is killing me … please understand … I’m sorry.

‘It wasn’t signed. And it didn’t make any sense. This disease?’

But it was enough to worry me. And of course, I thought of Beth. How could I not, given her history? Was she having suicidal thoughts?

‘I went into Beth’s room and turned on her computer. It wasn’t hard to find the document – there were several drafts of it. A notepad to the side of the keyboard was open, and I saw on the page various scribbles and I recognized at once the sharp peaks of the M. It was Melissa’s signature, or an approximation of it. The same scrawl I’d read year after year on birthday cards, Christmas cards, various notes.’

The feeling of unease was growing inside me, a panic starting in my brain as I clicked into the internet and opened the browser history.

‘It was all there,’ I tell Mark now. ‘Searches about fatal overdoses, about what quantities of various drugs would be required – sleeping pills, paracetamol, along with more specific searches about the various MS medications Melissa was taking. I couldn’t believe it. How forensic she had been. And her research seemed to have been going on for quite some time – there were scores of related searches.’

‘What did you do?’

‘I picked up the phone and called Melissa.’

I remember the coldness that came over me – like being doused in icy water. I felt it penetrating right through to my very heart. Because I knew she would not answer. Already, I knew she was dead.