He reaches into his jacket pocket and takes out his phone and I think, yes, yes, this is good. He’s going to call someone – maybe he had a massive row with them earlier today and he’s going to apologise, or demand an apology – either way, he’s going to make a move to fix it, this thing that has been the last straw and brought him to this place. Or maybe, when you’re in his state, all you need is the sound of another human voice, even a voicemail, the sound of your mum saying, ‘We’re not able to come to the phone right now but please leave a message after the tone.’ Maybe that’s enough to stop someone doing the thing they genuinely believe themselves about to do that they really don’t want to do at all.

He doesn’t make the call, not that call or any call. He looks at the phone’s screen, a blank, incurious glance, then slips the phone back into his pocket and I have a sudden, horrible image of the detective sergeant who will hold the phone and flick through his messages and the call register – that’s if it survives the wheels of the train. Don’t. That’s what I would text him, if I could. Please please don’t.

Or do. And you will be mine.

It comes to me then, the possibility that his fate is mine to decide. Perhaps – who knows? – that’s what I’m here for. Maybe that’s the way it works. This must be illusory – surely I don’t have that power – but I can’t shake the thought. People who attempt suicide and fail sometimes report hearing voices just beforehand, urging them on. Do it, stupid, you’ll never amount to anything. The world would be a better place without you in it. If I really want Caleb, or want to stand a chance of him, I could lean down now and whisper in his ear, just like I did to the woman queuing for her ticket last week. I’m sure she heard me.

I hover in front of him. Do I want him to live or die? If I let him live, he will go on to have a life – marry, perhaps, if he isn’t married already, have children, work, play, grow old. He will do all that without me … he won’t even think of me because he’ll never even know that I exist. Go on, Caleb, go on … why not? One moment and it will all be over. They won’t miss you. They don’t care. One moment, that’s all it will take.