‘You called her?’ It was stupid, but I didn’t want John talking to her. She had been out of my league even before I started vomiting and shedding, and I hadn’t got a clue what I would do even if John stepped back and waved me on. But still. Even though he was my friend, a small mean voice complained that he already had every good thing. Mia shouldn’t be on his list of acquisitions, too.

‘She called me!’ He grinned, showing perfect white teeth that I felt an unaccountable urge to punch. ‘Anyway. Gotta go. And you, you have to show on Saturday or we’ll all come here and crowd in like sardines.’ He got up, then paused at the door. ‘Oh, I almost forgot. You’ll like this one. In other news: Ian Rust got himself expelled! Devis won’t know what to do with himself with his mentor gone.’

‘Expelled?’ That really did bring a smile to my face. ‘What did he do?’

John frowned at that. ‘Twisted David Steiner’s arm up behind his back so far that something snapped.’

‘Something?’ My stomach went cold.

‘A bone.’

‘And nobody tried to stop him?’

‘Mr Roberts did. But Rust just broke Steiner’s arm anyway, and then pulled a knife on Roberts.’

‘Holy crap! Rust’s a fucking lunatic.’ Mr Roberts was a PE teacher, over six feet tall and packed with muscle.

‘Indeed.’ John nodded. ‘The police were called, but Rust had vanished by the time they came. Besides, they won’t hold him, just set a court date or something . . .’

When John had gone I turned on my reading lamp and returned to my textbooks. It was that or go downstairs to watch Dallas with Mother. She said it was her guilty pleasure, and it was true that it was about the only programme that would convince her to watch something other than BBC2. Even the instigation of a fourth channel hadn’t managed to do that!

I had to admit that quantum mechanics was clever stuff. Most of it danced to its own tune, but there was still enough fundamental mathematics underlying all the pretty manipulations to keep me interested.

I’d done what Demus said to do. After all, he had driven his fist into Devis’s over-loud mouth for me. And what else was there to do? I’d been presented with a mystery. I could focus on that, or I could worry about leukaemia chewing its way through the marrow of my bones. No contest really. Quantum mechanics wasn’t exactly easy, but it unravelled itself a lot more willingly than the strangeness that Demus constituted. Who the hell was he? Why had he singled me out? And why now?

Getting off school was easy. Escaping the house, harder. I’d taken the tube to South Kensington and hobbled my way past the Natural History Museum to Imperial College, an ugly set of buildings poured out of concrete mixers in the sixties, right behind the Royal Albert Hall.

I’d tried to get into the library first, picking up a leaflet from the main reception, but was escorted from the premises by an efficient woman with grey-streaked hair scraped into a tight bun and those angular glasses that they must force librarians to wear. Apparently, teenagers in Joy Division T-shirts were not welcome, and I should be in school. Though how she could distinguish me from the students, I didn’t know. And what kind of rowdy youth plays truant to come to a university physics library?

Professor James had seemed rather surprised to see me at his door. He asked me if I were lost. I answered by asking him if he had considered the Ryberg Hypothesis in non-Euclidian manifolds above five dimensions, because it suddenly became provable, and that fact had powerful implications for high order knot theory. After that, he was all mine.

To me the most interesting thing was, for once, not about the mathematics, but about the fact that Demus had known both that I was aware of the professor’s work in the area, and that I’d made several advances on what James had published.

‘This is quite extraordinary, young man.’ The professor sat down heavily, leaning back from our pages of scribbling. He had a habit of tugging at himself when he concentrated and now looked as if he’d been pulled backwards through a hedge. ‘Nicholas Hayes, did you say?’

‘Nick.’

He pulled at the corner of his moustache. ‘No relation to Alfred Hayes, of course?’

‘My father.’

‘Ah . . .’ He seized at that like a drowning man. ‘This is his unpublished work? I must say, I’m tremendously impressed that you understand any of it, Nick. What are you, first year, second?’

‘Actually, I’m not at the university yet. Which, uh, brings me to the real reason for my visit. I need to borrow your library card. Also, if you could call down to the librarian to expect me, that would help a lot.’

All I had to do was promise to come back with any more of my father’s papers that I might find, and Professor James couldn’t get his card into my hands quickly enough.

‘Nick?’ A knock at my bedroom door. I lifted my head from Quantum Mechanics and Path Integrals by Richard Feynman, the world’s greatest living expert on the subject. Another knock. I had the feeling there might have been several already that I failed to notice.

‘Yes?’

Mother opened the door. ‘You have another visitor.’ She sounded a little odd.

‘Hi, Nick!’ Mia squeezed past Mother, who had positioned herself as guardian of the doorway. ‘I bought chocolate brazils. They’re kinda like grapes. Only chocolate, and . . . not.’ She put the box beside me on the bed.

‘Uh . . .’ I blinked up at her. She wasn’t in uniform. I’d assumed she went to Elton’s school, but had never asked. Instead, she was gothed-up to eleven: black, black, more black, and some zips; black-circled eyes in a white face, lips a very dark red. ‘Hi.’

Mother stayed where she was, her smile fixed in that way we Brits use to show we wholly disapprove of something.

‘Hi.’ I said it again because suddenly it was all I had. I also became painfully aware that my woolly hat was just beyond arm’s reach, and that putting it on now would be too obvious. Instead, I had to treat her to the full patchwork horror show of my scalp.

‘Hi,’ Mia said. And then, just as I thought we might be locked in this death-spiral of greeting for the rest of our lives, ‘What you reading?’

Instead of answering, I looked pointedly over her shoulder at Mother, who had already outstayed the sociably acceptable linger limit by a factor of at least three. ‘I’d love a drink, Mum.’

She missed a beat at ‘Mum’ but rallied herself admirably. ‘Orange ju—’

‘Tea, please.’ I’d never asked for tea before.

‘Of course.’ Her smile re-fixed itself. ‘And . . . Mia? Would you like some . . . tea?’

‘Coffee, if you have it.’ Mia smiled. ‘White with two sugars.’

Mother retreated. I waited until I heard her footsteps on the stairs.

‘Quantum mechanics.’ I held up the book.

‘Cool.’ Mia sat on the bed. Closer than friends normally sit next to friends. She smelled of patchouli oil. I liked it. ‘What’s that about then?’

‘Well . . . it’s about everything, really. It’s the most accurate and complete description of the universe we’ve ever had. It’s also completely bonkers.’ I hesitated. I was pretty sure this wasn’t what you were supposed to talk about when girls came to visit.

‘More bonkers than general relativity?’ Mia took the book from the death grip I had it in. ‘The twins paradox is hard to beat.’

With a sigh, I relaxed. She was one of us! The magical power of D&D to draw together people who knew things. Who cared about questions that didn’t seem to matter.

‘Way weirder.’ Mia was right, the twins paradox was hard to beat. When Einstein showed the world that time was made of rubber and could be stretched for one person and squeezed for another until their lives were years out of kilter . . . that had been pretty strange. But even Einstein had balked at the cosmic strangeness quantum mechanics throws at us. ‘I’ve been looking at the many worlds interpretation.’

Mia started to open the box of chocolate brazils. ‘Go on.’

‘Well. The thing is, quantum mechanics is chock full of crazy, but every prediction it makes is perfect to as many decimal places as we can measure. Loads of our technology is built on it. Consequently, we just have to swallow the madness.’

‘Right.’ Mia pushed a chocolate past her lips, then offered the box to me.

‘What helps a bit is that you can move the crazy around depending on how you interpret the theory. None of the predictions change, and the crazy doesn’t go away: it’s just that the mad thing you’re asked to accept as the price of entry changes.’