‘It’s better than that,’ I say. Breslin raises a questioning eyebrow. ‘We’ve been looking for a motive, or at least something that could’ve triggered the attack. Right?’

Breslin blows air out of one corner of his mouth. ‘Well. You have. I still don’t actually care why he did it, as long as we can show that he did it.’

‘Rory gets over to Aislinn’s place,’ I say, ‘all amped up for the big night. He’s a bit early, but that’s no big deal; she lets him in, they’re delighted to see each other. And then, somehow, the stalking comes out. Maybe he lets something slip that tells Aislinn he knows Stoneybatter. Or maybe she mentions having seen him around the area, and he doesn’t cover it fast enough.’

It feels good, coming up with a story. I can see why everyone’s so hooked on it. I’ve got the whole scene playing out in front of me like another video clip, but one I can tweak and nudge till everything about it suits me right down to the ground. ‘Either way, Aislinn’s not happy. She’s already been having doubts about how full-on Rory is; she dismissed those, but this takes him over the line into whacko territory. She tells him to leave, and he loses the head.’

Breslin has his lips pursed and he’s nodding away. ‘I like this,’ he says. ‘I like it a lot. Conway, I think you’re onto something here. I knew there was a reason I had faith in you.’

I say, ‘Let’s see what Rory thinks of it.’

Breslin smiles at me, a great big warm smile like I’m the best thing he’s seen in months. ‘Come on,’ he says. ‘Let’s get out of here. This place stinks.’

I could drink the air in the corridor in one swallow, after that snot we’ve been breathing. Breslin shuts the incident-room door behind us with a neat contemptuous slam that says, You won’t be needing this place any more.

Back in the incident room, I ring Rory and ask him, all friendly and casual, if he would mind giving us a hand by coming in for another quick chat. I’m all ready to knock down a bunch of excuses about how he can’t leave the shop and he’s got an appointment and he doesn’t feel well, but he falls over himself agreeing to come in straightaway. He’s just desperate to prove he’s on our side, but I’m so unused to things being easy that it feels unnatural, almost creepy, like the world has slid a notch sideways and won’t click back to reality. I want sleep, a lot of it.