They were alone. Not another car in sight. No tractors or Land Rovers, no other drifters on the high plains, no fellow travellers at all. No farmhouses or sheep-barns either, only grass and barren limestone and a dead December sky. He was on the road to nowhere.

There were still a lot of hardy sheep wandering around though, aloof to the dangers posed by a bloody great Discovery bearing down on them. They must surely lamb late up here on these wuthering heights. Jackson wondered if they were already carrying next year's lambs. He had never considered the gestation period of a sheep before, it was surprising what a lonely road drove you to. His daughter had recently announced her conversion to the vegetarian cause. In a word association test his automatic response to the word 'lamb' would be 'mint sauce', Marlee's would be 'innocent'. The slaughter of. She was being brought up as an atheist, but she spoke the language of martyrs. Perhaps Catholicism was genetic, in the blood.

'Becoming a vegetarian seems to be a rite of passage for teenage girls these days,' Josie said, during his last visit to Cambridge at the end of the summer. 'All her friends have given up meat.' No more father-daughter bonding over a burger then.

'I know, I know, meat is murder,' he said, as they sat down at a table in a cafe of Marlee's choice called something like Seeds or Roots. ('Weeds,' he called it, to her annoyance.) He had had a hankering for a beef and mustard sandwich but settled for a chewy brown roll with an anaemic-looking filling that he guessed to be egg but which turned out -horror of horrors -to be 'scrambled tofu'.

'Yum,' he said and Marlee said, 'Don't be so cynical, Daddy. It suits you too much.'

When had his daughter started speaking like a woman? A year ago she had skipped along like a three-year-old on the path by the river to Grantchester (where, if his memory served him rightly, she had eaten a ham salad in the Orchard Tea Room, no guilt at all about ingesting Babe). Now, apparently, that girl had run on ahead out of sight. Turn your back for a minute and they were gone.

When you had children you measured your years in theirs. Not 'I'm forty-nine' but 'I have a twelve-year-old child'. Josie had another child now, another girl, two years old, the same age as Nathan. Two children united by the common thread of DNA they shared with their half-sister, Marlee. Just because Nathan didn't look like him didn't mean he wasn't his son. After all, Marlee didn't look like him either. Julia claimed that Nathan wasn't his child but when had anyone ever believed anything that his ex-girlfriend said? Julia was born to lie. Plus she was an actress, of course. So when she looked him earnestly in the eye and said, 'Really, Jackson, the baby isn't yours, I'm telling the truth, why would I lie?' his instinct was to say, 'Why change the habit of a lifetime now?' Instead of arguing (I generally only argue with people I like, she had once said to him), she had given him a pitying look.

He wanted a son. He wanted a son so he could teach him all the things he knew, as well as how to learn all the things he didn't know. He couldn't teach his daughter anything, she knew more than he did already. And he wanted a son because he was a man. Simple as that. He suddenly recalled the surge of emotion he had felt when he touched Nathan's head. That was the kind ofthing that made a strong man weak for life.

And anyway, he had said to Josie, since when was twelve a teenager? ' "Teen" is the clue -thirteen, fourteen, etcetera. She's only twelve.'

'Double figures count; Josie said casually. 'They start earlier these days.' 'Start what?' Jackson had passed through his teens without ever being aware of them. He had been a boy at twelve and then he had joined the army at sixteen and become a man. Between the two he had walked in the valley of the shadow of death, with no comfort to hand.

He hoped his daughter would have a sunny passage through those years. He had a crumpled postcard from her in the pocket of his jacket from when she had been on a school trip to Bruges in her half-term. The postcard showed a picturesque view of a canal and some old red-brick houses. Jackson had never felt the need to go to Belgium. He had transferred the card from his old leather jacket to the North Face jacket -his disguise -although from no clear motive, only that a message from his daughter, banal and dutiful though it was (,Dear Dad, Bruges is very interesting, it has a lot of nice buildings. It is raining. Have eaten a lot of chips and chocolate. Missing you! Love you! Marlee XXX'), seemed like something you shouldn't just throwaway. Did she really miss him? He suspected her life was too full to notice his absence.

A ragged-looking sheep, long-in-the-tooth mutton, stood foursquare in the road ahead, like a gunslinger waiting for high noon. Jackson slowed to a stop and waited it out for a while. The sheep didn't move. He hooted his horn but it didn't even twitch an ear, just continued chewing grass laconically like an old tobacco hand. He wondered if it was deaf. He got out of the car and looked at it threateningly.

'Are you gonna pull those pistols or whistle "Dixie"?' he said to it. It looked at him with a flicker of interest and then went back to its incessant chewing.

He tried to shift it bodily. It resisted, leaning its stupid weight against his. Shouldn't it be frightened of him? He would be frightened of him if he was a sheep.

Next he tried moving its hindquarters, to get some grip and torque, but it was impossible, it might as well have been cemented into the road. A headlock also got him nowhere. He was glad there was no one around to witness this absurd wrestling match. He wondered about the ethics ofpunching it. He backed off a few steps to rethink his tactics. Finally he tried pushing its front legs from beneath it but he ended up losing his own balance and found himself sprawled on his back on the road. Across the pale winter sky an even paler cloud floated overhead, as white and soft as a little lamb. From his prone position, Jackson watched its progress from one side of the dale to the other. When the cold had not only seeped into his bones but had begun to freeze the marrow inside them, Jackson sighed and, getting to his feet, he saluted his opponent.

'You win,' he said to the sheep. He climbed back in the car, turned on the CD player and put on Enya. When he woke up there were no sheep anywhere.

He was definitely off the map now. The sky was leaden, threatening snow. Higher and higher, heading for the top and some mysterious summit. The celestial city. It was a gated road and it was laborious having to get out of the car and open and close the gates each time. He supposed it was a way of corralling the sheep. Were there shepherds still? Jackson's idea of a shepherd was a rough-bearded man, wearing a home-made sheepskin jerkin, seated on a grassy hillside on a starlit night, a ram's-horn crook in hand as he watched for the wolves creeping on their bellies towards his flock. Jackson surprised himself with how poetically detailed and completely inaccurate his image of a shepherd was. In reality it would be all tractors and hormones and chemical dips. And the wolves were long gone, or, at any rate, the ones in wolves' clothing were. Jackson was a shepherd, he couldn't rest until the flock was accounted for, all gathered safely in. It was his calling and his curse. Protect and serve. Snow poles at the side of the road measured up to three metres.

He cast a wary eye at the sky, he wouldn't like to get stuck in a drift up here, no one would ever find you. He would have to dig in until spring, fleece a couple of sheep for blankets. No one knew he was here, he hadn't told anyone he was leaving London. If he was lost, if something happened to him, there was no one who would know where to come and look. If someone he loved was lost he would stalk the world for ever looking for them but he wasn't entirely sure that there was anyone who would do the same for him. (J love YOli, she said, but he wasn't sure how tenacious an emotion that was for her.)