After forcing myself to calm down, think it through, I decided I couldn’t. My first instinct was to protect my daughter, and that meant I didn’t want to do anything until I’d spoken to her and Emma. I wanted to talk to Fiona too. Find out why she’d been at Iris’s yesterday night, confident I would know if she was lying. Only then, if I thought I knew what was going on, would I talk to the police. Despite the whispering voice in my head, I was sure Rose and Fiona must have gone to wish Iris a good trip, that was all. A coincidence. They’d probably had a lucky escape, getting out before the violent intruder turned up.

I tried ringing Emma again as we walked over to the house but, again, it went to voicemail. I tried Rose too, and got the same result.

We entered the house and Lola ran up to us, tail wagging furiously.

‘Did they not give you an indication where they were going?’ I asked Dylan.

‘No. Mum just said they were going out. That was it.’

‘What time was this?’

‘I don’t know. I was still in bed. She spoke to me through my bedroom door and then I went back to sleep.’

This was what he did pretty much every day in the school holidays. I’d been the same when I was his age. A nocturnal animal.

I paced around helplessly.

‘Don’t you have us all on that family location app?’ he said.

‘Oh my God. Of course.’

When we’d bought Dylan and Rose their phones, I had installed an app that meant Emma and I could see where they were. All the parents I knew were the same. It was one of the positive things about teenagers and phones; we parents didn’t have to rely on them letting us know their whereabouts. Emma and I both had the app, which meant we could also both tell where the other was.I had very rarely used it to locate Emma, even at the darkest points of my paranoia about Mike, because it told the other person if you’d checked up on them. Now, though, I had good reason to look.

I opened the app.

‘What the hell?’ Dylan and I were listed as part of our family group, but Emma and Rose were missing. I handed my phone to Dylan, deferring to his teenage technological superiority. ‘Does this mean they’re offline?’

He scrutinised it. ‘No, it means they’ve deleted themselves.’

‘But Rose can’t delete hers without the password, can she?’

He shook his head. ‘Mum could do both, though.’

Dylan handed the phone back and I stared at the screen. ‘Why would she?’

‘I don’t know.’

I thought I might be sick. Maybe now was the time to go out and talk to the police. I was still reluctant, though, just in case Rose was involved with something criminal. I needed to do more to figure out what was going on first. Also, I felt certain the police wouldn’t take it seriously yet, not unless I told them I thought Fiona and Rose might know something about Iris’s death.

I took deep breaths to try to calm myself down, then went to the tap in the kitchen to fill a glass of water, taking it into the living room. From there I could see Iris’s house, the cops swarming around. The space where I’d stood talking to Tommy and Nicola.

What exactly had he said about Fiona last night?Don’t ever try to take her photo. She’ll freak right out.

Emma had speculated this was because Tommy was a creep who’d tried to spy on his female neighbour, a perv taking pics over the fence. But what if it was something else? I remembered my own attempts to research Fiona Smith online and my efforts to jog Iris’s memory.

‘She doesn’t want anyone to know who she is.’

‘What?’ Dylan said.

I hadn’t realised I’d spoken out loud, but now that I’d said it a terrible notion struck me. Had Iris remembered who Fiona was? And revealed this to Fiona?

Had Fiona murdered her to keep her real identity secret?

Still unable to believe this might actually be the case, I said, ‘If you wanted to find out who someone was, how would you do it? Apart from searching for their name, I mean?’

Because I was almost certain now that Fiona Smith was a fake name.

I didn’t need to wait for the answer. Tommy had provided it already. I said it aloud: ‘You’d take their photo. Show it around, maybe put it on social media ...’