Dismally he manipulated the injured tooth back and forth, feeling the broken surfaces grind together like shattered crockery. The tactful, near-subliminal voice of the flight attendant at his shoulder made him pull out his finger with an audible plop. “Have you got any painkillers?” Hayden asked, knowing in advance what the answer would be. Regret-fully, the attendant explained the airline’s strict policy with regard to passenger medications. Hayden nodded despondently, and stared out of the window at the cumulus clouds below. They looked like brilliant white molars in the cerulean gums of some unimaginably huge sky-troll.

The first actual sensations of pain had kicked in just prior to landing, after some four hours of incessant fiddling (tongue and fingertip) and an ill-advised glass of ice-cold mineral water. On the shuttle in from the airport his cheek had begun to puff out; once in his hotel room he’d hooked open his mouth in front of the bathroom mirror, fearing the worst. And finding it, in spades. Hard up against the gum-line there was a lump roughly the size and colour of a cherry tomato. It was hurting so badly, Hayden suspected it might actually be throbbing, visibly and palpably. Fully aware of what a stupid idea it would be, he inserted both index fingers, bracketed the swelling, and squeezed experimentally. The resultant right-hook of pain sent him staggering back from the mirror, cursing and whimpering through a mouthful of abscess and hurt.

In this way Hayden spent most of his first night in Hong Kong: alternately checking out the site of the damage in the mirror and pressed against the window in search of distraction. The waxing moon rose over the Island, soared across the tops of the skyscrapers and plunged into the fuzzy sink of light pollution above the western districts. Hayden followed its progress like a wounded timber wolf, baying with each pulsing wave of toothache, the pain as relentless and regular as the jets that slid across the night sky, heading for Lantau and the International Airport.

He was up in plenty of time for his nine o’clock at Chen 2000 Industries. Unfortunately, between the sleeplessness and the jet lag, he looked like a homeless man who’d sneaked in off the street to panhandle cash in the atrium. With some difficulty—everyone at Chen 2000 spoke excellent English, but he was starting to sound more and more like the Elephant Man—he went through his sales pitch, careful not to let his molars clash as he spoke. Suffice it to say that the case for fast-surface gate conductors from England could have been better put. On the way out he tried to make a joke of it all, pointing ruefully to his swollen cheek, and was rewarded with polite nods and smiles from the junior executives assigned to see him off the premises. Their smooth uncaring faces had showed marginally more interest in his PowerPoint slides and sales patter.

If the first night had been bad, then the second had been raw torture. As part of his duties, he’d been obliged to attend a banquet in the company of several important clients. Torn between not eating, which he understood would be disrespectful to the local culture, and eating, which he knew would probably end in tears, he’d chosen the latter, and had gingerly inserted a dressed tiger prawn into the opposite side of his mouth from the shattered tooth. Even before the chopsticks had cleared his lips the magnitude of his mistake became apparent. The hot hoi sin had sluiced around his tender mouth and gone straight to the root of the infection, where it had cut clean through the various analgesic treatments he’d been able to score from the pharmacy next door to the hotel. Like a dental probe wielded by some Nazi Doctor Death, the chili sauce skewered straight into the flaming abscess. The pain that ran up the outraged nerve nearly split his head in two.

His involuntary moan of anguish had turned heads all around the table. Passing it off as a cough hadn’t really helped, since even the slightest movement of his head was by now enough to make it feel as if his jaw was about to crack apart. Desperately, he’d searched the platters spread out before him for something—anything—he could reasonably appear to be eating (his plan was to nibble round the edges, and to smuggle the rest of it into his napkin), but whatever wasn’t marinaded in chilli appeared to be crispy and/or chewy, and neither option was feasible for Hayden in his current predicament. He’d spent the evening with one hand clamped to his jaw, as if trying to suppress the mother of all belches. From time to time a more than usually vile blast of pain would cause him to make a squashy razzing noise like an electrical buzzer under water, which he suspected was unacceptable in any social context the world over.

Somehow, he’d got back to the hotel. Things were starting to fray around the edges by this time, though no matter how much he drank the numbing edge of the alcohol never quite kicked in. It was the pain that was blurring things; that, and the killer sleeplessness. He’d made yet another raid on the nearby pharmacy, triple-dosed on everything (ignoring the compendious lists of contraindications in the packaging), then retired for another night of horrors.

Sleep was out of the question: he was unable to set his head down on the pillow, not even on the nominally good side. The ache oscillated between thumping pressure and piercing intensity, and by daybreak he’d felt so wretched that even the transition from one variety of pain to another—throb to stab—seemed like a relief of sorts. A grey-faced zombie leered back at him from the mirror. Was it possible, thought Hayden with the feverish, lachrymose wretchedness of a small child, for someone’s entire head to go septic?

The next day he didn’t even want to think about it. Don’t go there. And the night? Well, the night—

“Sir?” The nurse materialised at his side. “Dr. Pang will see you now.” Hayden nodded cautiously, and followed her through the translucent screens, carrying with him the copy of Scientific American from reception.

Dr. Pang was a neat young man in immaculate whites who projected a powerful, slightly inhuman air of professionalism. Shaking his hand, Hayden found himself wishing he’d flossed more thoroughly, changed his shirt before leaving the hotel, and generally lived a better life. To his credit, the dentist spoke excellent English and seemed genuinely concerned for his patient. So he should at the price, Hayden reflected ungenerously.

He settled back in a high-tech treatment chair, tilted and swivelled to the precise pitch of accessibility; the gas-cylinder hydraulics of the chair, with their all-but-imperceptible hiss at each resettling, were probably the noisiest pieces of equipment in the surgery, which otherwise resembled nothing so much as the sterile assembly room at Intel—assuming, that is, Intel were keeping on top of all the latest thinking in interior design.

“So, Mr. Hayden.” Dr. Pang perched on an adjustable stool at the side of the treatment chair, leaned slightly forward after the fashion of a father-confessor. “What seems to be the problem?”

Hayden settled back, taking absent-minded pleasure in the soft creak of the leather. He stared at the suspended ceiling, the gleaming baffled louvres of the light diffusers, and wondered where to begin. “I had this toothache,” he began; and then thought: God, the toothache, yeah. What about that? Where does pain go, when it goes? We remember the fact of its having happened: rationally, its existence is accessible to us as a memory, and all the rest of it. But does the body itself remember on some cellular level, tissue, meat and pulp? Not in the same way, or else we’d surely go crazy. Imagine if each component part of us had 24/7 sentience in its own right, equal broadcasting time, like candidates in the Presidential debate. Suppose each bone, each nerve ending, had its own hotline to the sensorium; imagine the clamour, as the body became a Grand Central of sensation, a Babel of reaction . . .

“A toothache?” Dr. Pang was waiting patiently. Hayden blinked, and tried to pick up his thread. “Er, sorry, yes. It started about a month ago, I suppose, just as I was arriving in Hong Kong.”

“A month? My goodness.” Dr. Pang was the picture of respectful sympathy. “Four weeks is a very long time to be in pain. Was it perhaps not so bad at first?”

“No . . . I mean yes. It was very painful.” If the Eskimos have all those words for snow, supposedly, then how come extreme discomfort boils down to a single syllable? True pain is irreducible, probably; indivisible, unchanging at the root. There are modifiers, quantifiers, stabbing and throbbing, acute and severe and all the rest of them, but they really just serve to dress up the thing in itself: the monad constant and impregnable, the primordial principle of existence. Ouch. It hurts, therefore I am.

Dr. Pang’s alert expressive face settled into a troubled moue. He shook his head slightly, as if in reproof. “Then you should have come to see me before now. Have you taken anything for the pain?”

Hayden felt in his pockets for the mangled remains of the various blister packs he’d picked up at the pharmacy, and handed them to Dr. Pang to be tutted over. “I was going through those a strip at a time at one point,” he confessed, resettling himself in the dentist’s chair. “Popping them like M&Ms. The thing was, none of them were really working.”

“Of course not.” Dr. Pang was shaking his head again, more in sorrow than in anger. “Over-the-counter medications such as these: you cannot expect them to deal with severe neuralgic pain. The problem must be dealt with at the root, Mr Hayden. Literally, in this case.” He allowed himself an unpresumptuous smile.