Huw opened the door and gave me a hug, munching a Chinese radish. 'Mo! You got here! Sorry I couldn't meet you at the airport... If John had given me a little more warning, I'd have rescheduled my day.'

'h.e.l.lo, Huw. It was plain sailing until I got to your building. I thought the fourth floor meant the third floor. Or the third, the fourth. Anyway, your neighbour put me right.'

'Hong Kong's never quite sure of itself. British or American or Chinese numbering, even I still get muddled. Come in, put down your bag, have some tea and a bath.'

'Huw. I don't know how to thank you for this.'

'Nonsense. Us Celts have got to stick together. You're my first house-guest, we'll have to make things up as we go along. Come and inspect your quarters. Not a patch on your chalet, I'm afraid-'

'My ex-employer's chalet-'

'Your ex-employer's chalet. Here you are! Chez Mo. Cramped and messy, but it's yours, and unless the CIA has c.o.c.kroaches on its payroll they'll never find you.'

'In my limited experience the CIA has a lot of c.o.c.kroaches on its payroll.'

The room was no more cramped or messy than fifty labs I'd worked in. There was a sofabed ready for me to crash on, bless Huw, a desk, stacks of books that would bury me with one mild earth tremor, and a vase of flamingo orchids. 'The lavatory's through there, if you stand on it and twist your neck around you get a cracking view of Kowloon harbour.'

It was as humid as a launderette. Hives of life rumbled on the other sides of the floor, walls and ceiling. The tenement across the alley was so close that our window frames seemed to share the same gla.s.s. Trains grinded, little things scuttled, and somewhere a giant bicycle pump was cranking itself up and hissing itself down.

The life of a conscience-led scientist. 'It's perfect, Huw. Can I use your computer?'

'Your computer,' insisted Huw. computer,' insisted Huw.

The fire in the kitchen hearth wheezed and popped. Liam and I looked at one another, suddenly at a loss. The tiles chilled my toes. I'd polished this reunion for so long, but now I could only gawp. I remembered baby goblin Liam, I remembered the adolescent mutant he'd been last summer with b.u.mfluff on his top lip, and I saw the raffish man he'd make in a decade or two. As well-summered as you can get in Dublin, his hair was gelled, he'd got an ear stud and his jaw was squatter.

'Mam-' his voice had become a ba.s.soon.

'Liam-' I said at exactly the same time, my voice a flautist's mistake.

'Oh for the love of G.o.d you two,' muttered John.

It was suddenly all right and Liam was hugging me first and hardest. I hugged back harder and until we both groaned, but that wasn't why I wanted to cry. 'You're supposed to be at Uni, you malingerer. Who gave you permission to grow so much in my absence?'

'Ma, who gave you permission to do a James Bond G.o.d-knows-where in my my absence? And who did that to your eye?' absence? And who did that to your eye?'

I looked at John around Liam's shoulder. 'You have a point. I'm sorry. A knight in shining armour did this to my eye. I forgave him. He'd knocked me out of the path of a taxi.'

'"A point", she calls it Da, you hear that?'

I karate-chopped his sides.

'Don't I get an apology too?' whinged John.

'Shut up, Cullin,' I said, 'you're only the father and you don't have any rights.'

'I'll just go and blunder off a cliff then and leave you two to it.'

'Happy birthday! Da! Sorry I couldn't get back last night. I stayed at Kevin's in Baltimore.'

'Blame your ma. She only phoned from London yesterday morning.'

'I can't do anything to her. She's bearhugging me.'

'You just have to wait until it pa.s.ses.'

I let Liam go. 'Off with your coat and sit by the fire. The fog's made you clammy. And don't tell me those ridiculous s.p.a.ceman trainers keep your feet dry. Now tell me about university. Is Knyfer McMahon still Faculty Head? What are you doing for your first-year thesis?'

'No, Ma, no! I haven't seen you for half a year, with only your voice on tapes. Where have you you been and what have been and what have you you been doing? Tell her, Da!' been doing? Tell her, Da!'

'John Cullin, did you teach our son to answer back to his elders and betters?'

'You just have to wait until it pa.s.ses. Anyway, I'm only the father. Tea?'

Liam sniffed. 'Please.'

Planck was still running around in nervous wagging circles.

In my first week in Hong Kong, I did very little. I got lost and unlost and lost in byways and overways and underways. A quarter of the world, teeming in a few square miles. Huw was right. If I avoided computer link-ups I was probably untraceable. But after Switzerland I felt I had crash-landed on a strange planet where privacy and peace were coincidences rather than rights. 'Dispense with the niceties,' advised Huw, 'and learn to do inside your head what you can't do outside.'

I got a fake British pa.s.sport made, for only fifty US dollars.

I watched the television war. I watched the weaponry a.n.a.lysed, hyped and billed: Scud versus Homer, Batman versus the Joker. The war had been 'won' days before, the supply of cheap oil secured, but that was no longer the point. Technology efficacy needed to be tested in combat conditions, and to use up stockpiles. The wretched army of conscripts from the enemy's ethnic minorities were the laboratory rats. Quancog's laboratory rats. My laboratory rats.

I recorded a tape of me and Hong Kong, and posted it to John, via Siobhan in Cork, John's Aunt Triona in Baltimore, Billy, Father Wally and thus to John. I prayed it would get through undetected, a snail invisible to radar.

Huw was suddenly dispatched to Petersburg, so there I was: alone, unknown, unemployed, a box of hundred-dollar notes concealed in the freezer compartment under bags of peas. My escape plan had worked too well. No kidnapper from phantom crime networks so much as dropped in for a chat. Had the Texan just been bluffing? Trying to scare me to Saragosa?

Now what?

We create models to explain nature, but the models wind up gatecrashing nature and driving away the original inhabitants. In my lecturing days most of my students believed that atoms really are solid little stellar nuclei orbited by electrons. When I tell them that n.o.body knows what an electron is, they look at me like I've told them that the sun is a watermelon. One of the better read-up ones might put up their hand and say, 'But Dr Muntervary, isn't an electron a charged probability wave?'

'Suppose now,' I am fond of saying, 'I prefer to think of it as a dance.'

Forty summers ago, two miles away from Aodhagan Croft. There is a c.h.i.n.k in the floorboards in the upstairs room of the house in the sycamores. After I've been put to bed, I sometimes pull back the rug and look down into the parlour. My ma wears her white dress and her cultured pearls, and Da a black shirt. On the gramophone revolves a new 78 rpm from Dublin.

'No no no, Jack Muntervary,' Ma scolds, 'you've got two left feet. Elephant ones.'

'Chinatown, my Chinatown,' crackles the gramophone.

'Try again.'

Their shadows dance on the walls.

What now, indeed?

I was still a physicist, even if n.o.body knew it but me. The idea crept up and announced itself while I was haggling down the price of grapefruits in the market. Pink grapefruits pink as dawn. Strip quantum cognition down to first principles, and rebuild it incorporating nonlocality, instead of trying to lock nonlocality out. Before I'd paid for the grapefruits, ideas for formulae were kicking down the door. I bought a leather-bound black notebook from a stationer's, sat down next to a stone dragon and scribbled eight pages of calculations, before I spilt them and lost them.

In the days and weeks following my routine grew saggier but regular. I got up around one in the afternoon and ate at a dim sung dim sung restaurant across the alleyway. The place was owned by an old albino man. I sat in the corner with restaurant across the alleyway. The place was owned by an old albino man. I sat in the corner with The Economist, Legal Advisor The Economist, Legal Advisor, a Delia Smith cookery book, or whatever else was lying around Huw's apartment. On lucky days the shoeshiner who was the de facto de facto postman for our tenement had a jiffy bag addressed to Huw with a tape from John. I listened to them in my postman for our tenement had a jiffy bag addressed to Huw with a tape from John. I listened to them in my dim sung dim sung corner on Huw's Walkman, over and over. Sometimes John had recorded new compositions, or lines from his new poems. Sometimes he'd just record a busy night in The Green Man. Sometimes sheep, seals, skylarks, the wind turbine. If Liam were home there would be some Liam. The summer fayre. The Fastnet Race. I would unfold my map of Clear Island. Those tapes prised the lid off homesickness and rattled out the contents, but always at the bottom was solace. corner on Huw's Walkman, over and over. Sometimes John had recorded new compositions, or lines from his new poems. Sometimes he'd just record a busy night in The Green Man. Sometimes sheep, seals, skylarks, the wind turbine. If Liam were home there would be some Liam. The summer fayre. The Fastnet Race. I would unfold my map of Clear Island. Those tapes prised the lid off homesickness and rattled out the contents, but always at the bottom was solace.

At the end of the afternoon I sat down at the rickety desk and picked up from where I had left off in the early hours. I worked in isolation: e-mailing any of the handful of people alive who could have contributed was too dangerous. It was liberating: not having to be accountable to Heinz Formaggio and other cretins. I had my father's fountain pen, my black book, a box of CDs containing data from every particle lab experiment ever conducted, and thousands of dollars of computer equipment bought from a Sikh gentleman more resourceful than Light Box Procurement. Compared to Kepler, who plotted the ellipsoids of Mars with little more than a goose quill, I had it easy.

There were wrong turnings. I had to jettison matrix mechanics in favour of virtual numbers, and my doomed attempt to amalgamate the EinsteinPodolskyRosen paradox with Cadwalladr's behavioural model set me back weeks. It was the loneliest time in my life. As chess players or writers or mystics know, the pursuit of insight takes you deep into the forest. Days were I'd just gaze at the steam rising from my coffee, or stains on the wall, or a locked door. Days were I'd find the next key in the steam or the stains or the lock.

By July all the footprints of Einstein, Bohr and Sonada were behind me.

The black book was filling up.

I was still talking. Liam's toast had gone cold. A helicopter flew over.

What is Liam thinking?

Is it, 'Why can't I have normal parents?'

Is it, 'Will she never stop?'

'Is my ma a madwoman?'

It makes me sad that I can't read my son's thoughts. There again, it's right this way. He's eighteen, now. I missed his birthday again. Where will I be for the next one?

'Well don't stop there, Ma. You're just getting to the good bit.'

The strong force that stops the protons of a nucleus hurtling away from one another; the weak force that keeps the electrons from crashing into the protons; electromagnetism, which lights the planet and cooks dinner; and gravity, which is the most down to Earth. From before the time the universe was the size of a walnut to its present diameter, these four forces have been the statute book of matter, be it the core of Sirius or the electrochemical ducts of the brains of students in the lecture theatre at Belfast. Bored, intent, asleep, dreaming, in receding tiers. Chewing pencils or following me.

Matter is thought, and thought is matter. Nothing exists that cannot be synthesised.

Summer. Huw came back late most nights, to s.n.a.t.c.h a few hours of sleep before returning to his office. A securities firm had crashed, and the effects were rippling out. Sometimes a week went by and apart from noticing the toothpaste tube depleting we were barely aware of one another. On Sundays, however, we always dressed up and went out to dinner somewhere expensive, but low-key. I didn't want to risk meeting his colleagues. Lying is a skill I have never mastered.

I often worked all night. Hong Kong never really quietens down, the sunlight just switches off for a few hours. Huw's snores, the G.o.dalmighty clatter of Kowloon's sweat shops, that gigantic bicycle pump, the eye of the electric fan and moth wings on the computer screen ushered in the quantum mathematics of sentience.

Three sharp knocks on John's door and a mantrap snapped shut, I'd jumped up, spilt my tea and was crouched in the stair doorway, poised to run where? Only one door I would have to jump from the second floor and run for it across the meadows. Great idea, Mo. Dislocate a hip. Liam didn't know what was going on. John was working it out, my panic bashing its head on his defences.

'It's okay, Ma-' Liam began.

I sliced the air. 'Sssssh!'

Liam showed me the palms of his hands like he was calming a scared animal. 'It's either Father Wally, Maisie or Red come to milk Feynman...'

I shook my head. They'd have knocked once, if at all, and walked in.

'Who was on the St Fachtna St Fachtna with you this morning? Any Americans?' with you this morning? Any Americans?'

There was another rattle of knocking. 'h.e.l.lo?' A woman. Not Irish, not English.

I put my finger over my lips, and tiptoed up the stairs. They creaked.

A mouth to the letterbox. 'G'day? Anyone home?'

'Morning to you,' said John. 'Just a moment...'

I slid into the bedroom and looked for somewhere to hide the black book. Where, Mo? Under the mattress? Eat it?

I heard John opening the door. 'Sorry to keep you.'

'No worries. Sorry for the bother. I'm walking to this row of stones on the map here. Map-reading was never my strong point.'

'The stone row? Piece of cake. Go back down the drive, turn left, and just follow the sign to Roe's bridge. All the way until the road peters out. Then you'll see it. Unless the mist has other plans.'

'Thanks a million. Too bad about this rain, eh? It's like winter back home.'

How can John be so calm? 'Where is home? New Zealand?'

'That's right! Halfmoon Bay, Stewart Island, south of the South Island. Know it?'

'Can't say I do. 'Fraid the weather's a law unto itself, here. Tropical rainstorms, raining frogs... Gales later though, the fishing forecast said earlier. Winter's around the corner.'

'Just my luck. Say now, you're a lovely dog! A him or a her?'

'A her. Planck.'

'As in thick as a?'

'As in the physicist who discovered why you can sit in front of a fire and not be incinerated by the ultraviolet catastrophe.'

Nervous laugh. 'Oh, right, that that Planck. Mild-mannered beastie for an island dog.' Planck. Mild-mannered beastie for an island dog.'

'It's her job. She's my guide dog.'

The usual awkwardness. I relaxed. A pursuer would know about John. Unless she was just a good actress. I tensed up.

'You mean, er, you're...'

'...as a bat. A lot blinder than a bat, actually. I'm unequipped with sonar.'

'Strewth... there was I... I'm sorry.'

'No need.'

'Well, I'd better get to the row of stones before the gales blow 'em over.'

'Take your time. They've been there three thousand years. Mind how you go.'