2. The Library

Next morning, sober and triumphant, Jim said with stunning precision: ‘Saturday, four o’clock. Café in Central Library.’

Brenda frowned, and Jody said if she couldn’t stop me going she was coming too, and Mike said he’d be there if I needed him – Brenda and Jody exchanged an amused and cynical glance – he’d be in the Social Sciences reading room.

But when we came down the library basement steps, the place was empty and the café had just closed.

We hung around a bit, but no one came, and as we went back up to say hello to Mike, I had the feeling of having been hoaxed.

That circular reading room foxes me every time: you think you’re still walking away from the point where you entered when you realise you’re approaching it again. There was Mike at the end of one of the long radiating tables, and Magda, who’d been shopping and was leaning towards him over his book about the Chartists and her many chain-shop bags and informing him in a hiss that no, he couldn’t count the Welfare State, we British had never known true revolution because in order to be effective revolutions had to be violent and quick. And – she put up her hand imperiously to stop him - he destroyed his own case to cite Peterloo, the classic mistake of a peaceful demonstration which only results in further suppression, and what better symbol of this than the building now sitting on the site, a capitalist hotel.

Mike was mad. They weren’t whispering any more. I said ‘Ssh!’ though actually there was a louder group on the opposite side, hidden by the circular central desk, and the librarian was setting off to quieten them.

Jody had been distracted. ‘Listen!’ she said. As it happened, the other group stopped talking too. Somewhere close was a loud sound of tapping, yet when we looked round there was no one nearby. She pointed upwards. The tapping was coming off the dome above. Somewhere to our left someone ripped a sheet of paper, and then above and to our right the sound echoed, magnified. Like a whispering gallery: the other voices I’d been hearing had been our own.

I looked back down. A slim thirtyish guy with a wispy beard and a stripy woolly hat was coming round the central desk towards me, holding out a slip of paper. ‘From my friend. He’s sorry he didn’t show today.’ Someone else touched my arm and I whirled around, but it was only the librarian, who’d found the source of the noise at last. I looked back towards the guy and he’d gone.

Nowhere in the reading room, nowhere in the corridor.

Even I was a bit spooked then. And how did he know it was me, and where to find me just then? And get this: there was a scribbled mobile number, but whenever I ring it I get the voicemail service.

It’s like Brenda said yesterday: you just don’t know what’s what any more. She meant different things, actually: summer turned into autumn, ice caps melting, friendly fire, victims turned suspects (she’d just bought a paper plastered with photos of the McCanns).

But I mean: whoever this person is, is he looking for me or hiding?

Voting has now closed. Readers voted for Ahmed to play an important role in helping solve the mystery. Tune in on Tuesday to find out how.