‘I told him I would think about it, but that at present there were other, needier souls I must attend to. So I left him here and walked up this narrow lane.’ She pointed left, to where a ginnel cut away from the cobbled road, curving out of sight between outbuildings. ‘I’d gone maybe forty yards when I heard a motor vehicle engine revving, and a shouting – a loud shouting, as if there was a fight. I hurried back but all I saw when I got here was a vehicle pulling away along Canning Crescent. And no sign of Fred.’

‘A vehicle?’ Lucy said. ‘Had it been parked here when you came down the path?’

‘I didn’t notice it. But as you can see, there’s a shadowy area over there.’ The ex-nun pointed right, and about fifty yards away, a cement ramp tilted down through a square, garage-type aperture into what looked like a subterranean parking zone beneath the warehouse. At this time of night, what little light there was petered out at the entrance, so a vehicle could easily loiter there, just out of sight.

‘Did you see what kind of vehicle it was?’ Lucy asked.

‘Of course. It was a transit van.’

‘A transit van?’ A shiver scurried down Lucy’s spine. ‘What colour?’

Sister Cassie thought this over. ‘Dark. It was dusk, of course, but I’ve always been blessed with good eyesight. I’d say … purple maybe. Or blue. Yes, that’s it. Darkish blue.’

‘I don’t suppose you remember any part of its registration number?’

‘I never remember minor details, I’m afraid.’

‘Okay, fair enough. Look—’

‘Which is why I wrote it down.’

Lucy’s hair prickled. ‘You did?’

‘Well, the first part of it at least.’ The ex-nun rooted in her satchel. ‘I know I put it here somewhere.’

When she finally located it, she’d written five characters down on a condom wrapper, which she apologised for, but said was the only thing she’d found when she’d scrabbled around for something to write on. Lucy could only shake her head, fascinated by Sister Cassie’s resourcefulness. She gloved up and slipped the wrapper into a transparent plastic envelope, saying that it didn’t matter about the missing characters – this was more than enough for them to work with.

They headed back through the building together, the ex-nun guiding the police officer along open passageways, clear of rubble, which would have been far less frightening had she discovered these avenues for herself earlier. All the way, Lucy tried to get through to the PNC on her radio, though the signal broke repeatedly.