All day Richard Wilder had been preparing for his ascent. After the noise-filled night, which he had spent calming his sons and giggling wife, Wilder left for the television studios. Once there, he cancelled his appointments and told his secretary that he would be away for the next few days. While he spoke, Wilder was barely aware of this puzzled young woman or his curious colleagues in the nearby offices-he had shaved only the left side of his face, and had not changed his clothes since the previous day. Tired out, he briefly fell asleep at his desk, watched by his secretary as he slumped snoring across his unread correspondence. After no more than an hour at the studios, he packed his briefcase and returned to the high-rise.

For Wilder, this brief period away from the apartment building was almost dreamlike in its unreality. He left his car in the parking-lot without locking it and walked towards the entrance, a growing sense of relief coming over him. Even the debris scattered at the foot of the building, the empty bottles and garbage-stained cars with their broken windscreens, in a strange way merely reinforced his conviction that the only real events in his life were those taking place within the high-rise.

Although it was after eleven o'clock, Helen and the children were still asleep. A film of white dust covered the furniture in the lounge and bedrooms, as if he had returned to the apartment and its three sleepers after an immense period of time had condensed around them like a stone frost. Wilder had blocked the air-conditioning vents during the night, and the apartment was without sound or movement. Wilder looked down at his wife, lying on the bed surrounded by the children's books she was reviewing. Aware that he would be leaving her in a few hours, he regretted that she was too weak to come with him. They might have climbed the high-rise together.

Trying to think more clearly about his ascent, Wilder began to clean the apartment. He stepped out on to the balcony and swept up the cigarette butts and broken glass, condoms and torn newspapers thrown down from the floors above. He could no longer remember when he had made his decision to climb the building, and had little idea of what exactly he would do when he finally got there. He was also well aware of the disparity between the simple business of climbing to the roof-a matter of pressing an elevator button-and the mythologized version of this ascent that had taken over his mind.

This same surrender to a logic more powerful than reason was evident in the behaviour of Wilder's neighbours. In the elevator lobby he listened to the latest rumours. Earlier that morning there had been a serious brawl between the 9th- and llth-floor tenants. The 10th-floor concourse was now a no-man's land between two warring factions, the residents of the lower nine floors and those in the middle section of the building. Despite the harassment and increasing violence, no one was surprised by these events. The routines of daily life within the high-rise, the visits to the supermarket, liquor store and hair-dressing salon continued as before. In some way the high-rise was able to accommodate this double logic. Even the tone of voice of his neighbours as they described these outbreaks of hostility was calm and matter-of-fact, like that of civilians in a war-torn city dealing with yet another air-raid. For the first time it occurred to Wilder that the residents enjoyed this breakdown of its services, and the growing confrontation between themselves. All this brought them together, and ended the frigid isolation of the previous months.

During the afternoon Wilder played with his sons and waited for the evening to come. Helen moved silently around the apartment, barely aware of her husband. After the fit of compulsive laughter the previous evening, her face was waxy and expressionless. Now and then a tic flickered in the right apex of her mouth, as if reflecting a tremor deep within her mind. She sat at the dining-table, mechanically straightening the boys' hair. Watching her, and unable to think of what he could do to help her, Wilder almost believed that it was she who was leaving him, rather than the contrary.

As the light began to fade, Wilder watched the first of the residents return from their offices. Among them, stepping from her car, was Jane Sheridan. Six months earlier, Wilder had broken off a brief affair with the actress, ironically enough because of the effort involved in reaching the 37th floor. He had found it difficult to be himself in her apartment. All the time he was conscious of the distance to the ground, and of his wife and children far below him, deep in the lowest seams of the building like the exploited women and child labourers of the nineteenth century. Watching television during their sexual acts in her chintz-lined bedroom, he felt as if he were high over the city in a lavish executive airliner fitted with boudoir and cocktail bar. Their conversations, even their diction and vocabulary, had become as stylized as those of strangers in adjacent aircraft seats.

The actress walked to the private entrance of the upper-floor elevator lobby, picking her way casually through the broken bottles and empty cans. A single journey to her apartment would carry him, like a ladder in a board game, virtually to the top of the high-rise with one throw of the dice.

Helen was putting the boys to bed. She had moved the wardrobe and dressing-table around their beds, in an attempt to shield them from the noise and disturbances which the night would bring.

"Richard…? Are you going…?"

As she spoke she emerged briefly from the deep well inside herself, aware for these few seconds that she and her sons were about to be left on their own.

Wilder waited for this moment of lucidity to pass, knowing that it would be impossible to describe his self-imposed mission to Helen. She sat silently on her bed, a hand resting on the pile of children's books, watching him in the mirror with an unchanging expression as he stepped into the corridor.

Wilder soon found that it was more difficult than he had assumed to climb to the 37th floor. The five top-floor elevators were either out of order or had been taken to the upper levels and parked there with their doors jammed open.

The 2nd-floor lobby was crowded with Wilder's neighbours, some in office suits, others in beach wear, arguing with each other like disgruntled tourists caught by a currency crisis. Wilder pushed through them to the staircase, and began the long climb to the 10th floor, where he stood a better chance of finding an ascending elevator.

When he reached the 5th floor he met the dozen members of the airline pilots' raiding party returning from another of their abortive missions. Angry and shaken, they shouted at the people jeering down at them from the stairwell above. The entrance to the 10th-floor concourse had been blocked by desks and chairs taken from the junior school and flung down the stairs. The raiding party, made up of parents of the children attending the school, had tried to replace the desks, harassed by residents from the middle floors waiting impatiently for the liquor store to be re-stocked.

Wilder pressed on past them. By the time he reached the 10th floor the opposing group had moved off in a posse. Wilder stepped over the broken desks lying on the steps, pencils and crayons scattered around them. Wishing that he had brought his camera with him, he noticed two 18th-floor residents, a chemical engineer and a personnel manager, standing by the door. Each had a cine-camera and was carefully filming the scene below, following Wilder as he climbed towards them.

Leaving them to complete these dubious private news-reels, Wilder pushed back the swing doors, and looked out at the deck of the shopping mall. Hundreds of residents jostled against each other, pulling and shoving among the wine-bins and shelves of detergent packs, wire trollies locked together in a mesh of chromium wire. Voices rose in anger above the singing of the cash registers. Meanwhile, as these scuffles took place, a line of women customers sat under the driers in the hairdressing salon, calmly reading their magazines. The two cashiers on evening duty at the bank impassively counted out their bank-notes.

Giving up any attempt to cross the concourse, Wilder turned into the deserted swimming-pool. The water level was down by at least six inches, as if someone had been stealing the yellowing fluid. Wilder walked around the pool. An empty wine bottle floated in the centre, surrounded by a swill of cigarette packs and unravelling cigar butts. Below the diving-boards a newspaper hung slackly in the water, its wavering headline like a message from another world.

In the 10th-floor lobby a crowd of residents pressed impatiently against the elevator doors, their arms laden with liquor cartons and delicatessen purchases, raw materials for the aggressive parties of that evening. Wilder returned to the staircase. Somewhere above him these passengers would step out of their elevators and give him a chance to get aboard.

He climbed the steps two at a time. The staircase was deserted-the higher up the building the more reluctant were the residents to use the stairs, as if this in some way demeaned them. As he pressed on upwards Wilder peered through the windows at the car-park sinking from view below. The distant arm of the river stretched towards the darkening outline of the city, a signpost pointing towards a forgotten world.

As he turned into the final stretch of steps to the 14th floor, picking his way among the discarded cans and cigarette packs, something moved above his head. Wilder paused and looked up, his lungs pumping in the silence. A kitchen chair whirled through the air towards his head, hurled down by an assailant three floors above. Wilder flinched back as the steel chair struck the railing, glancing against his right arm before spinning away.

Wilder crouched against the steps, shielding himself below the overhang of the next floor. He massaged his bruised arm. At least three or four people were waiting for him, ostentatiously tapping their clubs on the metal railing. Fists clenching, Wilder searched the steps for a weapon. Danger in the streets of the sky-his first impulse was to rush the stairs and counter-attack. With his powerful physique he knew that he could put to flight any three residents of the high-rise, these under-exercised and overweight account executives and corporation lawyers egged on into this well-bred violence by their pushy wives. However, he calmed himself, deciding against a frontal attack-he would reach the top of the high-rise, but by guile rather than by brute force.