I wanted to find out. I don’t know why; maybe he looked like someone I thought I could get on with. I went up to him, during the break. I introduced myself, and he said his name was Marcus. ‘Hi,’ I said, and he smiled, and in that moment I realized just how attracted I was to him. It was a desire that felt solid, had a shape, a pull that felt physical. I’d never experienced it before, not like this. I wanted to reach out, to touch his neck, his hair, his lips. Just to be sure he existed, was real. ‘First time?’ I said, and he said yes, yes it was. We chatted for a while. Somehow – I don’t remember how, or even whether he volunteered the information himself – I learned that the girlfriend didn’t exist. He was single. When it was time to go back to our seats he came and sat next to me, and after the meeting we went outside. We paused to say goodbye, about to head off in different directions.

‘Are you here next week?’

He shrugged, kicked the kerb. ‘Probably.’ He turned to leave, but then he pulled a scrap of paper out of his wallet.

‘Got a pen?’ he said.

Was that it? I wonder now. Was that the moment my life slipped out of one track – recovery, stability, sobriety – and into another? Or did that come later?

I open my eyes. I can’t think of him any more. He belongs in the past; my family is here, now. My family is Hugh, and Connor.

And Kate.

I get up. This can’t go on, this waking up in the middle of the night. This avoiding of things. I’m haunted by the place she lost her life; I should’ve gone to see it when I had the chance, but there are other ways.

I go downstairs and sit at the kitchen table. I’m determined, I have to do this. In Paris I was a coward, but now I can put it right. I open my laptop and log on to the map programme. I type in the address.

I press enter. A map appears on the screen, criss-crossed with roads, scattered with points of interest. There’s an arrow dropped into it and when I click on Street View the map disappears, replaced by a photo of the road. It looks broad, lined with trees, with shops and banks and a stack of prefabs covered in graffiti. The photo has been taken during the day and the place looks busy; passers-by frozen as they walk along it, their faces blurred inexpertly by the software.

I stare at the screen. It looks ordinary. How could my sister have lost her life here? How could it have left no trace?

I steel myself, then navigate along the road. I see the alleyway, cutting down between a building and the raised railway line that crosses the road.

I’m here, I think. The place she died.

I zoom in. It seems anodyne, harmless. At one end there’s a kiosk, painted blue with a sign advertising Cosmétiques Antilles, and there are two rows of bollards dotting the pavement. The alleyway curves after what looks like four or five yards, and I can’t see down it.

I wonder where it leads, what’s at the other end. I wonder why there was no one there to save her and, for the millionth time, what she was doing there.

I need answers. I fetch the box that Anna gave me from under my bed and take it back downstairs. I look at the picture on the front, the woman in the red dress. For two months I’ve tried to ignore this, terrified of what I might find, but I can’t any longer. How bad can it be? I ask myself. Didn’t Anna say it was just some paperwork? That’s all.

Yet still I’m afraid. But what of? Evidence of how far she’d come, perhaps. Proof that she was right, that Connor would have been better back with her?

I take out her passport and hold it for a moment before putting it to one side. Underneath it there are some letters, and beneath them her birth certificate and driving licence, along with her medical card and a note with what I assume is her National Insurance number.

It calms me, somehow. I’m facing something that’s been waiting for me. I’m doing well. I feel surprisingly okay.

I dig further in. It’s more difficult; there are photos, taken at parties, one of Connor that I’d sent her, another of some friends on a boat trip along the Seine. I tell myself I’ll look at them properly later. Further down there’s a pink Filofax, pocket-sized. This seems hardest of all, but when I flick through its pages I see she seems to have stopped using it when she got an iPhone last summer. Tucked into it is a single sheet of paper. I take that out and unfold it.

Straight away I see a name I recognize. Written at the top is ‘Jasper1234’. It’s the name of the Labrador we had when we were little, followed by four digits, and next to it she’s written ‘KatieB’, and then a Web address, encountrz.com. The rest of the page is filled with a list of odd words – ‘Eastdude’; ‘Athletique27’; ‘Kolm’; ‘Ourcq’ – all written at different times, in different inks and with different pens. It takes me only a moment to piece it together. Encountrz is the site Anna told me about, the one they both used. Kate used our dog’s name as a password, KatieB as her username.

I refold the page and put it back. The guilt I’ve told myself I shouldn’t feel rolls again in my stomach. I should’ve looked at this sooner, I think. It might be important, something the police have missed. I’ve let her down; there was something I could’ve done to save her, something I could still do to make it all right.

I dial Anna’s number. It’s early, but this feels urgent. And it’s an hour later in Paris. Nearly six.

She answers almost immediately. Sleepy, anxious. ‘Hello?’

‘Anna? It’s me. Julia.’

‘Julia. Is everything okay?’

‘Yes, fine. I’m sorry to call so early. I didn’t mean to wake you, but that box you gave me? You’re sure the police have gone through it?’

‘Box? You mean Kate’s things?’

‘Yes. The police have definitely looked at it?’

‘Yes, I’m certain. Why?’

‘I’m just looking at it all now—’

‘Now? It’s very early …’

‘I know, but I couldn’t sleep. The thing is, there’s a list of names. I think they might be people she was talking to. Online, I mean. I thought the police should see them …’

‘They did, I think. They had everything in that box. They said they’d kept everything they might need.’

‘You’re sure?’

‘I think so, yes. Give me a second.’

She’s quiet for a moment; I imagine her shaking herself awake. ‘Sorry. What names are they?’

I read the first couple out. ‘Do any of them sound familiar? Did she mention any of them to you?’

‘No—’

I carry on reading. After a few more names she stops me. She’s wide awake now.

‘Wait. Did you say “Ourcq”? That’s not a username. It’s a Métro station.’

I know what she’s going to say.

‘It’s near where they found her body.’

‘So that’s what she was doing there? Meeting someone off this list?’

‘I don’t know,’ she says. But already I’m feeling a curious surge of energy. ‘But I guess it’s possible.’

I end the call. I look again at the list of usernames in her Filofax. It’s as if I’ve found a weak spot in the wall of my grief, something that might lead me first in and then through, on to the other side. To peace.

I wake my laptop. I type quickly: encountrz.com. I tell myself I just want to have a look. I can’t do any harm. I’m about to press enter when I hear a noise. A cough, then a voice.

‘Darling?’ It’s Hugh. ‘It’s half five in the morning. What on earth are you doing?’

I close the browser window and turn to face him. He’s wearing his gown, tied around his waist, and yawns as he rubs his eyes. ‘Are you okay?’

‘Yes. I couldn’t sleep.’

‘Again? What’s wrong?’

‘I just keep thinking the police must’ve missed something.’

He sighs. I say the same thing to him every single day.

‘I think they’re being incredibly thorough.’ He comes over and sits next to me. I know he can see what’s on my screen.

‘If I hear anything new I always tell you straight away. You know that.’