He says, ‘I don’t know. Just . . . making sure I could find the house, that kind of thing.’

I look puzzled. ‘But you said her place was practically around the corner from the bus stop. That sounds like you already knew your way around.’

Rory’s blinking hard. ‘What? . . . No – no, not like that. But Aislinn had given me directions. And I’d looked up the map on my phone. It wasn’t complicated. I just wanted to allow a little extra time, just in case.’

I leave a sceptical pause, but he doesn’t jump into it. ‘OK,’ I say. ‘So you got off the 39A in Stoneybatter – what time?’

‘A little before half-seven. There wasn’t much traffic.’

In plenty of time to reach Aislinn’s house, kill her, and be back outside the door knocking and looking confused by eight o’clock. It even makes sense of turning off the cooker: Rory didn’t want the fire alarm going off before he had time to act out his little play with the calls and the texts and presumably the worried pacing, for anyone who might be watching. That hot smell fills up my nose.

I glance over at the one-way glass, which stares blankly back. One look at Steve would have told me if his mind was matching mine. Instead I have Breslin, who’s rocking his chair on its back legs and doodling in his notebook. I think about kicking the chair out from under him.

‘You were well early,’ I say. ‘What’d you do?’

Rory says, ‘I walked round to the top of Viking Gardens – that’s Aislinn’s road. To make sure I had the directions right. Like I said.’

‘See anyone on Viking Gardens?’

‘No. The street was empty. I didn’t hang around there, though. I didn’t want anyone thinking I was a burglar or a, a stalker.’ Another jab at his glasses.

‘Did you go into the road? Find Aislinn’s house?’

‘No. It’s a straight road, a cul-de-sac – I could see the whole thing from the top; I didn’t need to find the house in advance. And I wasn’t keen on the idea of Aislinn looking out her window and seeing me there half an hour early. She would have had to invite me in, and she wouldn’t have been ready, and overall it would have been really awkward.’