I keep staring at the board as if the facts will change, but they don’t. I ask a station guard but all she can tell me is the exact same thing. I’ll have to wait almost fifty-five minutes. I am here, stuck, and Charlie is miles away in London, at school, and I won’t be able to get back in time and no one will be there when he comes out.

I send a text to the school, frantic with apologies, explaining. I’ll be there as soon as I can, I say.

I have never done this to Charlie before. I have always, always been there to pick him up, never late by more than a few minutes. I have done everything I can to be so reliable. Because when there is no one else, who can we rely on? But now I have gone off on an obsessive mission of my own, for Sarah, for myself, thinking I was fixing the whole world. And instead all I’ve done is let Charlie down.

I try and control my breathing. I go into the station toilets and splash water on my hot face, trying not to cry. I mentally send a million apologies to Charlie.

My phone blips. We can supervise him only until 4 p.m., the school texts back. Please ensure someone collects him by then.

I have to find someone to help me. But who? Who? I think of all the other parents: Sally and Rachel and Martin. Molly’s dad. Any of them would do, but when I scroll through my phone, I see I haven’t stored any of their numbers. I know there is a sheet of paper from the school that has all their contact details on it. But that is shoved in a drawer in my kitchen, and not an ounce of good to me now. I stare at my contacts list, so short, so limited. I don’t know what to do, I have no idea who to call.

Except maybe one person.

I can feel the wariness still lodged inside me, but what other choice do I have? For Charlie’s sake, I have to reach out. I open his number, desperately praying that he will be there. I pause, my thumb hovering over his name. I have to, don’t I? Despite the knots in my stomach?

I press call. And Alastair answers.

It comes out in a garble, the predicament I’m in, but it’s fine, he reassures me. He’s not at work, he can get there. I grow weak in the wave of relief.

Just text the school my details, he says, tell them who I am. Charlie has met him, he has the Silly Putty to remember. And Alastair is a good person, he works with children; surely he will be able to keep Charlie safe.