During these days after the drowning of the dog, the air of over-excitement within the high-rise gradually settled itself, but to Dr Laing this comparative calm was all the more ominous. The swimming-pool on the 10th floor remained deserted, partly, Laing assumed, because everyone felt that the water was contaminated by the dead Afghan. An almost palpable miasma hung over the slack water, as if the spirit of the drowned beast was gathering to itself all the forces of revenge and retribution present within the building.

On his way to the medical school a few mornings after the incident, Laing looked in at the 10th-floor concourse. After booking a squash court for his weekly game that evening with Anthony Royal, he walked towards the entrance of the swimming-pool. He remembered the panic and stampede during the blackout. By contrast, the shopping mall was now almost empty, a single customer ordering his wines at the liquor store. Laing pushed back the swing doors and strolled around the pool. The changing cubicles were closed, the curtains drawn across the shower stalls. The official attendant, a retired physical-training instructor, was absent from his booth behind the diving-boards. Evidently the profanation of his water had been too much for him.

Laing stood by the tiled verge at the deep end, under the unvarying fluorescent light. Now and then, the slight lateral movement of the building in the surrounding airstream sent a warning ripple across the flat surface of the water, as if in its pelagic deeps an immense creature was stirring in its sleep. He remembered helping the accountant to lift the Afghan from the water, and being surprised by its lightness. With its glamorous plumage drenched by the chlorinated water, the dog had lain like a large stoat on the coloured tiles. While they waited for the owner, a television actress on the 37th floor, to come down and collect the dog Laing examined it carefully. There were no external wounds or marks of restraint. Conceivably it had strayed from its apartment into a passing elevator and emerged on to the shopping concourse during the confusion of the power failure, fallen into the swimming-pool and died there of exhaustion. But the explanation hardly fitted the facts. The blackout had lasted little more than fifteen minutes, and a dog of this size was powerful enough to swim for hours. Besides, it could simply have stood on its hind legs in the shallow end. But if it had been thrown into the pool, and held below the water in the darkness by a strong swimmer…

Surprised by his own suspicions, Laing made a second circuit of the pool. Something convinced him that the dog's drowning had been a provocative act, intended to invite further retaliation in its turn. The presence of the fifty or so dogs in the high-rise had long been a source of irritation. Almost all of them were owned by residents on the top ten floors-just as, conversely, most of the fifty children lived in the lower ten. Together the dogs formed a set of over-pampered pedigree pets whose owners were not noticeably concerned for their fellow tenants' comfort and privacy. The dogs barked around the car-parks when they were walked in the evening, fouling the pathways between the cars. On more than one occasion elevator doors were sprayed with urine. Laing had heard Helen Wilder complain that, rather than use their five high-speed elevators which carried them from a separate entrance lobby directly to the top floors, the dog-owners habitually transferred to the lower-level elevators, encouraging their pets to use them as lavatories.

This rivalry between the dog-owners and the parents of small children had in a sense already polarized the building. Between the upper and lower floors the central mass of apartments-roughly from the loth floor to the 30th-formed a buffer state. During the brief interregnum after the dog's drowning a kind of knowing calm presided over the middle section of the high-rise, as if the residents had already realized what was taking place within the building.

Laing discovered this when he returned that evening from the medical school. By six o'clock the section of the parking-lot reserved for the 20th to the 25th floors would usually be full, forcing him to leave his car in the visitors' section three hundred yards from the building. Reasonably enough, the architects had zoned the parking-lots so that the higher a resident's apartment (and consequently the longer the journey by elevator), the nearer he parked to the building. The residents from the lower floors had to walk considerable distances to and from their cars each day-a sight not without its satisfaction, Laing had noticed. Somehow the high-rise played into the hands of the most petty impulses.

That evening, however, as he reached the already crowded car-park, Laing was surprised by his fellow tenants' tolerant behaviour. He arrived at the same time as his neighbour Dr Steele. By rights they should have raced each other for the last vacant place, and taken separate elevators to their floor. But tonight each beckoned the other forward in a show of exaggerated gallantry and waited while the other parked. They even walked together to the main entrance.

In the lobby a group of tenants stood outside the manager's office, remonstrating noisily with his secretary. The electrical supply system on the gth floor was still out of order, and at night the floor was in darkness. Fortunately it was light until late in the summer evening, but the inconvenience to the fifty residents on the floor was considerable. None of the appliances in their apartments would function, and the limits of co-operation with their neighbours on the floors above and below had soon been reached.

Steele watched them unsympathetically. Although he was in his late twenties, his manner was already securely middle-aged. Laing found himself fascinated by his immaculate centre parting, almost an orifice.

"They're always complaining about something," Steele confided to Laing as they stepped into an elevator. "If it isn't this, it's that. They seem unwilling to accept that the services in a new building take time to settle down."

"Still, it must be a nuisance to have no power."

Steele shook his head. "They persistently overload the master-fuses with their elaborate stereo-systems and unnecessary appliances. Electronic baby-minders because the mothers are too lazy to get out of their easy chairs, special mashers for their children's food…"

Laing waited for the journey to end, already regretting his new-found solidarity with his neighbour. For some reason, Steele made him nervous. Not for the first time, he wished he had purchased an apartment above the 30th floor. The high-speed elevators were bliss.

"The children here look well enough to me," he remarked when they stepped out at the 25th floor.

The surgeon held his elbow in a surprisingly powerful grip. He smiled reassuringly, flashing a mouth like a miniature cathedral of polished ivory.

"Believe me, Laing. I see their teeth."

The punitive tone in Steele's voice, as if he were describing a traditionally feckless band of migrant workers rather than his well-to-do neighbours, came as a surprise to Laing. He knew casually a few of the 9th floor residents-a sociologist who was a friend of Charlotte Melville's, and an air-traffic controller who played string trios with friends on the 25th floor, an amusing and refined man to whom Laing often talked as he carried his cello into the elevator. But distance lent disenchantment.

The extent of this separation of loyalties was brought home to Laing when he set off to play squash with Anthony Royal. He took an elevator up to the 40th floor and, as usual, arrived ten minutes early so that he could go out on to the roof. The spectacular view always made Laing aware of his ambivalent feelings for this concrete landscape. Part of its appeal lay all too clearly in the fact that this was an environment built, not for man, but for man's absence.

Laing leaned against the parapet, shivering pleasantly in his sports-clothes. He shielded his eyes from the strong air currents that rose off the face of the high-rise. The cluster of auditorium roofs, curving roadway embankments and rectilinear curtain-walling formed an intriguing medley of geometries-less a habitable architecture, he reflected, than the unconscious diagram of a mysterious psychic event.

Fifty feet away to Laing's left a cocktail party was in progress. Two buffet tables covered with white cloths had been laid with trays of canapés and glasses, and a waiter was serving drinks behind a portable bar. Some thirty guests in evening dress stood about talking in small groups. For a few minutes Laing ignored them, absent-mindedly tapping his rackets case on the parapet, but something about the hard, over-animated chatter made him turn. Several of the guests were looking in his direction, and Laing was certain that they were talking about him. The party had moved nearer, and the closest guests were no more than ten feet away. All were residents from the top three floors. Even more unusual was the self-conscious formality of their dress. At none of the parties in the high-rise had Laing seen anyone dressed in anything other than casual wear, yet here the men wore dinner-jackets and black ties, the women floor-length evening dresses. They carried themselves in a purposeful way, as if this were less a party than a planning conference.

Almost within arm's reach, the immaculate figure of a well-to-do art dealer was squaring up to Laing, the lapels of his dinner-jacket flexing like an over-worked bellows. On either side of him were the middle-aged wives of a stock-exchange jobber and a society photographer, staring distastefully at Laing's white sports-clothes and sneakers.

Laing picked up his rackets case and towel bag, but his way to the staircase was blocked by the people around him. The entire cocktail party had moved along the roof, and the waiter now stood alone between the bar and the buffet tables.

Laing leaned against the parapet, for the first time conscious of the immense distance to the ground below. He was encircled by a heavily breathing group of his fellow residents, so close that he could smell the medley of expensive scents and after-shaves. He was curious as to what exactly they were going to do, but at the same time was aware that at any moment a meaningless act of violence might occur.

"Dr Laing… Ladies, would you release the doctor?" At what seemed the last moment, a familiar figure with adroit hands and a soft walk called out reassuringly. Laing recognized the jeweller whose hysterical wife he had briefly examined during the power failure. As he greeted Laing the guests casually dispersed, like a group of extras switched to another scene. Without thinking, they strolled back to their drinks and canapés.