‘Get off, Mum!’ Bic protested, deciding that enough was enough. He ducked under her arm and past her into the flat, but only because she didn’t contest it.

‘Children are the treasure house of the world,’ Mrs Daniels declared, favouring me with a self-conscious but sincere smile. The fact that I’d seen her in her parental role seemed to have broken the ice between us in some decisive way.

I nodded, returning the smile. ‘Shouldn’t he be in school?’ I asked, mainly for the sake of prolonging the moment of trust and intimacy.

‘Baker day,’ Mrs Daniels said, with a roll of the eyes. ‘In-service training. All the secondary schools are closed today. It’s lucky I’m on a late shift, isn’t it? God knows how other mothers cope. I’m sorry, but I’ve really got to go now. Nice to meet you, Mister . . .’

For a moment I considered giving her a false name, since my real one clearly hadn’t stuck either time. There might possibly be some point in lying, if Basquiat came gunning for me in earnest and wanted to establish an evidence trail.

But I gave the detective credit where it was due: she wouldn’t stay in the dark for long if she seriously wanted to check up on me.

‘Castor,’ I said, making the hat trick. ‘Felix Castor.’

‘Good day to you, Mister Castor. I’ll tell Mister Seddon you were looking for him.’

The door closed in my face - all the way, this time. Tom’s needs had to be met, and clearly Mrs Daniels had no more time for small talk. I stood in the corridor for a few moments longer, trying to make sense of what she’d said. Clearly something ha wi somethd happened to Kenny recently. Something bad, that had left a permanent shadow - or had seemed to. Something he could perhaps have prevented, because there were signs in advance that other people had been able to see.

It was probably unrelated to the attack on him, of course - and the odds were overwhelming that it had no bearing at all on why he’d written my name in his own blood as he sank into unconsciousness and possibly into death.

But I had to start somewhere, and if I couldn’t cajole the truth out of the neighbours I knew someone I could buy it from at the market price.

I went back into the daylight at last, and it was welcome. There was something oppressive about the interior of the tower that made me grateful to see the sun again, even if it was beating down like a hammer on an anvil. A wounded-ox lowing of distant traffic met my ears, audible again because I’d been out of it for ten minutes. The miasma was becoming harder to sense for the opposite reason - because it was holding steady now, and my senses were starting to tune it out.

I might as well carry on north, I thought - maybe pick up the Tube at Elephant and Castle. I headed on along the walkway, past more bin bags and a bike that had been chained to a lamp post with a D-lock and then deprived of its wheels to deter theft. Unless the wheels had been stolen to deter cycling."

"I saw the same sigil again - the teardrop with its corona of radiating lines, this time executed in red paint - on the parapet wall.

Next to it, spray-painted on the grey cement of the walkway itself, were the words NOW IT BLEEDS. The words were also done in red, and they looked fresh and new in this faded place. I crossed to look at them, then squatted down and touched the curve of the final S. Very fresh: the paint was still wet.

From this vantage point, I noticed for the first time that the concrete slabs of the parapet wall had been set with narrow gaps in them every few feet. The gaps afforded a view of the lower walkway beneath me and then the ground, where Bic’s friends - or maybe a different group of boys entirely - came briefly into view on their way to somewhere that probably wasn’t any better than here.

Someone on the lower walkway was watching them, or at least looking out in that direction. He was standing right up against the parapet, his back to me. He wore a raincoat of pure unblemished white that recalled Alec Guinness as Sidney Stratton, the Man in the Ice Cream Suit, and his sleek, possibly brilliantined black hair stood out all the more starkly against it.

There was something indefinably familiar about that black-white contrast, and about the man’s ramrod bearing; his refusal to lean against the parapet even though it was right there, at the perfect leaning distance and height. I had a presentiment that was nothing to do with my death-sense.

Another man walked into my severely restricted field of vision and joined him. This guy was big and rangy and looked subtly out of proportion: but then I was seeing him from an odd angle. His face was almost completely flat, as though he’d made humorous Tom-and-Jerry-style contact with a frying pan. When he spoke, his mouth opened across its full width in a way that looked strained and awkward, the lips not moving at all.