Looking up suddenly, I pull my arm away, my eyes darting across the room.

‘Where did they come from?’

He raises his arms. ‘Isobel, seriously, I have no idea. Someone left them with Elaine at reception. I just picked them up on my way in—’

Before he can finish his sentence I’ve pushed through the door to reception. Elaine’s empty desk and a well-worn doormat are the only thing between the office and the world beyond.

‘What …?’ My hands fly to my cheeks, and my whole body shakes as I run to the front door, flinging it open and looking out at the flood of people moving back and forth across the street, my eyes searching for something they cannot find.

Si has to roar to make himself heard above the din of the World’s End pub. He speaks slowly, picking up one of the glasses of whisky on the table between us. You have to drink quickly in this place to forget the stench of stale sick and rancid beer.

‘So let me get this straight … You’re saying that this guy, whoever he is, murdered a woman in the middle of Hampstead Heath, then saw you watching them, somehow found your shoes, discovered where you work and then brought them to your office.’

‘I didn’t say murdered.’ My eyes are fixed over Si’s shoulder, scanning the figures passing back and forth, I’m vaguely aware of my feet tapping at hyper-speed against the sticky surface of the floorboards. Si looks at me, taking another slug of his drink.

‘OK, attacked … I mean, fucking hell, Is, this is nuts. Have you been to the police?’

I nod; the motion of my foot tapping against the floor causes the table between us to vibrate.

‘What did they say?’

‘Fuck all.’ My jaw is tense, I need a cigarette.

He looks like he wants to probe further, but thinks better of it. ‘OK, look. I’m not saying you’re exaggerating at all, but for a moment – just bear with me – ask yourself: why would he do that? If someone attacked a woman on the Heath and he saw you and for whatever reason he knows where you work, and he found your shoes … Why would he return them to the office?’

There is a pause.

‘You think I’m making it up?’

‘No, Issy, of course I don’t. I’m not saying that – I just said I’m not saying that … I’m just asking why. Why would he do that? We need to think.’ His voice softens as he leans in, trying to catch my eye. ‘You’re a reporter, surely you’ve already asked yourself that question?’

‘Of course I have, you patronising prick. I don’t know, Si, maybe because he’s a psychopath?’ I hiss, looking up at him and shaking my head. ‘Maybe it was a warning, his way of telling me that he knows where I am?’