Alastair glances at me, sensing the awkwardness. ‘Oh wait! Here.’ He digs in his pocket and pulls out a little green tub. ‘I don’t really know if you’re into this,’ he says, squatting down in front of my son, ‘but the kids on the ward love this stuff.’

It’s Silly Putty. Such a fun, innocent thing. From the start, didn’t I know that Alastair was a kind person? A good person. He came to find me, to check I was okay, and he knew I’d be with Charlie so he brought him this toy.

Charlie looks up at me, checking it’s okay. I nod to him: go on. He takes the little present from Alastair shyly.

‘It was nice to meet you, Charlie,’ Alastair says, getting back to his feet.

‘Say thank you,’ I tell Charlie. ‘Tell him thank you before you go.’

Charlie doesn’t have a father in his life, and so he does far more than that. He puts his arms right around Alastair and hugs him. I rub my eyes, feeling so exhausted.

And I watch as Alastair hugs him right back.

I feel steadier after that, though. At least I think I do. And so when I get to my desk in the office, I don’t even wait to switch on my computer before I try calling the number on the postcard. I can still hear the voice in my head: Forget all this. You’re getting in too deep, but it’s like an addiction, I can’t stop. The further reality seems to retreat, the more desperate my need for answers grows. I tap the numbers from the back of the postcard into my phone and press dial.

I don’t think I seriously expected it to ring.

I don’t think I seriously expected anyone to pick up.

So when the voice comes on the line – Hello, Chloe speaking – I nearly lose hold of the phone in surprise. ‘Chloe?’ I repeat.

‘Yes – who is this, please?’ Her voice is soft but very clear. She could be standing right next to me.

‘My name is Jennifer,’ I say, ‘Jennifer Arden. You don’t know me, but I’m a … a contact of your old friend Sarah Jones.’

Of course there’s a silence then on the line. ‘… Sarah?’

‘I understand you knew each other?’

‘Yes. We were … at high school together. Excuse me, who did you say you were?’

‘I’m sorry … I was … I am the manager for the flat Sarah rented. And I also knew her, very briefly, through work.’ I switch the handset to my other hand. ‘Chloe, I’m sorry, but could we meet up? I’m not sure I want to explain this over the phone.’

‘Explain what? I’m sorry, I’m not following. I’m not even sure how you … even have this number.’