I said, ‘We stick around much longer, McKenna’s going to get onto your gaffer.’

Conway didn’t look up from her phone. ‘I know, yeah. She said that to me, down in Arnold’s room. Didn’t even bother being subtle: told me if we weren’t out by dinnertime, she’d ring O’Kelly and tell him we bullied her students into fits.’

‘It’s dinnertime now.’

‘Chillax. I wasn’t subtle either. I told her if she tries to throw us out before we’re good and ready, I’ll ring my journalist pal and tell him we’ve spent the day interviewing Kilda’s students about Chris Harper.’ Conway shoved her phone into her pocket. ‘We’re going nowhere.’

I could’ve backslapped her, hugged her, something. I didn’t want my nads kicked in. ‘Fair play to you,’ I said, instead.

‘What, you thought McKenna was gonna make me her bitch? Thanks a bunch.’ But the big grin on me pulled one out of her, too. ‘So. Meanwhile . . .’

I said, ‘Joanne?’

Conway took a breath. Behind her, the curtains stirred; the cutlery mobile made a faint high ringing, soft and faraway.

She nodded, once. ‘Joanne,’ she said.

I said, ‘Witness or suspect?’

A suspect, you need to caution her, get her to sign a rights sheet, before you go asking any questions. A suspect, you take her down to HQ, get everything on video. A suspect, if she wants a solicitor, she gets one. An underage suspect, you have an appropriate adult present; you don’t even think about dodging.

Just now and again, we fudge it. No one can prove what you’re thinking inside your own mind. Once in a long while you keep it casual, just a chat with a witness, till your suspect gets in too deep for you, or him, to deny.

If you get caught out, if the judge gives you a filthy look and says any officer with half a brain would’ve suspected this person, then you’re done. Everything you got, gone: thrown out.

We were on the line. Plenty of reasons to think it might be Joanne; not enough to believe it was.

‘Witness,’ Conway said. ‘Be careful.’

I said, ‘You too. Joanne’s not about to forget that you took her down a peg in front of the rest.’

‘Ah, for fuck.’ Conway’s head tossing up with irritation: she’d forgotten. ‘That’s me stuck in the back seat again. Next time we need to piss someone off, I’m gonna make you do it.’

‘Ah, no,’ I said. ‘You do it. You’ve got a gift.’ The face she made at me looked like a friend’s.

In the common room the girls were neat around tables, heads bent over plates, homey rhythm of clinking cutlery. The nun had one eye on her food and one on them.