After outlining what he expected to read next year in the third IPCC report, Aldous told Beard – and was the fiftieth person to do so in the past twelve months – that the last ten years of the twentieth century had been the warmest ten, or was it nine, on record. Then he was musing on climate sensitivity, the temperature rise associated with a doubling of CO2 above pre-industrial levels. As they entered London proper, it was radiative forcing, and after that the familiar litany of shrinking glaciers, encroaching deserts, dissolving coral reefs, disrupted ocean currents, rising sea levels, disappearing this and that, on and on, while Beard sank into a gloom of inattention, not because the planet was in peril – that moronic word again – but because someone was telling him it was with such enthusiasm. This was what he disliked about political people – injustice and calamity animated them, it was their milk, their lifeblood, it pleasured them.

So climate change was consuming Tom Aldous. Did he have other subjects? Yes, he did. He was concerned about the emissions from his car and had found an engineer in Dagenham who was going to help him convert it to run on electricity. The drive train was good, the problem was the battery – he would need to recharge it every thirty miles. He would just about make it into work if he travelled no faster than eighteen mph. Finally, Beard forced Aldous into the human arena by asking him where he lived. In a studio flat at the bottom of his uncle’s garden in Hampstead. Each weekend he drove to Swaffham to visit his father, who was ill with a lung infection. The mother was long dead.

The story of the mother was about to begin as they pulled up outside the house. Beard was interrupting to speak his thanks, keen to bring the encounter to an end, but Aldous was out of the car and hurrying round to open the passenger’s door and help him out.

‘I can manage, I can manage,’ Beard said testily, but with the recent weight-gain, he almost could not, the wretched car was so low-slung. Aldous accompanied him up the path, again in psychiatric-nurse style, and when they were at the front door and Beard was reaching for his key, asked if he might use the lavatory. How to refuse? Just as they stepped into the house he remembered that it was Patrice’s afternoon off, and there she was, at the head of the stairs, in rakish blue eyepatch, tight jeans, pale green cashmere sweater, Turkish slippers, coming down to meet them with pleasant smiles and the offer of coffee as soon as her husband had made the introductions.

For twenty minutes they sat at the kitchen table, and she was kind, she cocked her head sweetly as she listened to the story of Tom Aldous’s mother and asked sympathetic questions, and told the story of her own mother, who also died young. Then the conversation lightened, and her eyes met Beard’s whenever she laughed, she included him, she listened with a half-smile when he spoke, appeared amused when he made a joke, and at one point touched his hand to interrupt him. Tom Aldous was suddenly blessed with expressiveness and humour, and made them laugh with an account of his father, a formidable history teacher, now a cantankerous invalid, who fed his hospital lunch to a ravenous red kite. Aldous kept turning away and grinning, and self-consciously running his hand up his neck to touch his ponytail. At no point did he remember that the planet was in peril.

And so the married couple harmoniously entertained the merry young man, and by the time he stood to leave it was clear that something wondrous had happened, there had been a fundamental shift in Patrice’s attitude towards her husband. After seeing Aldous to his car, Beard, not daring to believe that his plan, summoning a woman on the stairs with his bare hands, had actually worked, hurried back into the house to learn more. But the kitchen was deserted, the cups with their dregs were still in place on the table, the house was quiet again. Patrice had retreated to her room, and when he went up and tapped on her door she told him plainly to go away. She had only wished to torment him with a glimpse of the life they once had. It was her absence she wanted him to savour.

He did not catch sight of her until the following evening, as she left the house, leaving behind a trail of unfamiliar scent.

The weeks passed and little changed. The autumn term began at Patrice’s primary school. In the early evenings she marked work and prepared classes, and three or four times a week left the house around seven or eight to be at Tarpin’s. When the clocks went back in late October and she went up the garden path in darkness, her absence was all the more complete. Nothing came of her intention to have her lover round to dinner, at least, not while Beard was in the house. Occasional meetings took him out of town for the night, and when he returned he saw no sign of Tarpin’s presence, unless it was in the deeper sheen of the oak dining-room table or the neatness of the kitchen, with every pot and pan unusually stowed.

But in early November he went into the walk-in larder at the rear of the house, near the back door, in search of a light bulb. It was a cold and windowless room with brick-and-stone shelves where various household hardware and junk and unwanted presents had spilled into the space intended for provisions. On the far wall was a single ventilation slot which showed pinpricks of daylight, and directly underneath, on the floor, was a dirty canvas bag. He stood over it, letting his outrage grow, and then, noticing that the top was undone, parted it with his foot. He saw tools – different-sized hammers, bolsters and heavy-duty screwdrivers and, lying right on top, a chocolate-bar wrapper, a brown apple core, a comb and, to his disgust, a crumpled used paper tissue. The bag could not have been left behind when Tarpin was working on the bathroom, for that was many months back and Beard knew he would have seen it. It was clear enough. While he was in Paris or Edinburgh, the builder had come straight from work to see Patrice, had forgotten his tools the next morning, or did not need them, and she had stowed them in here. He wanted to throw them out immediately, but the handles of the bag were black and greasy, and Beard felt revulsion at touching anything of Tarpin’s. He found the bulb and went into the kitchen to pour himself a scotch. It was three in the afternoon.

Early the next day, a cold Sunday, he found Rodney Tarpin’s address on an invoice and, after deciding not to shave and drinking three cups of strong coffee, and pulling on a pair of old leather boots that added an inch to his height and a thick woollen shirt that put muscle on his upper arms, he drove towards Cricklewood. On the radio, exclusively American affairs. Commentators were still picking over last month’s bombing of the warship USS Cole by a group called al-Qaeda, but the main item was the same old thing, it had run all summer and autumn and was wearing on his patience. Bush versus Gore. Beard was not an American citizen, he had no vote in this fight, and still was obliged by the news service, for which he was compelled to pay a fee, to attend to every bland development. He was aggressively apolitical – to the fingertips, he liked to say. He disliked the overheated non-arguments, the efforts each side made to misunderstand and misrepresent the other, the amnesia that spooled behind each ‘issue’ as it arose. To Beard, the United States was the fascinating entity that owned three quarters of the world’s science. The rest was froth and, in this case, a struggle within an elite – the privileged son of a former president jostling with the high-born son of a senator. With the polls long closed, it seemed, Gore had phoned Bush to retract his concession of defeat, Florida was too close to call, there would be an automatic recount – ‘Circumstances have changed since I first called you’ was the understatement Al Gore had used.