When he woke the next morning he once again heard the intruder’s breathing, so rested that his mysterious visitor seemed almost to be part of everyday life in the solarium. Sure enough, as Pangborn had expected, all the modest traps had been sprung. The man had washed his hands with the fresh bar of soap, a small portion of the steak and salad had been eaten, a strange footprint marked the talc in the bathroom.

Unsettled by this tangible proof that he was not alone in the solarium, Pangborn stared at the footprint. The man’s foot was almost the size of his own, with the same overlarge and questing big toe. Something about this similarity brought a flush of irritation to Pangborn. He felt a sudden sense of challenge, provoked by this feeling of identity with the man.

This close involvement with the intruder was redoubled when Pangborn discovered that the man had taken a book from his shelf — the almost unobtainable text of the original dialogue of The Third Man, now a cautionary tale put out by the world tourist authority on the perils of the language barrier. Pangborn thumbed through the pages of the scenario, half-hoping to find a further clue to the man’s identity. He carefully replaced the book on the shelf. These first hints of the intruder’s nature — the shared literary tastes, the shape of his feet, the sounds of his breathing and his body smell — both intrigued and provoked him.

As he played at high speed through the hours of film the solarium camera had recorded, he now and then caught what seemed to be brief glimpses of the intruder — the flash of an elbow behind the bathroom door, a shoulder framed against the medicine cabinet, the back of a head in the hall. Pangborn gazed at these magnifications, expanding them beside the stills from Psycho, the systems of two parallel but coinciding geometries.

This never explicit but civilized duel between them continued during the next days. At times Pangborn felt that he was running a mnage-a-deux. He effectively cooked meals for them both — the intruder fortunately approved of Pangborn’s tastes in wine, and often reinforced the night with small measures of Pangborn’s brandy. Above all, their intellectual tastes coincided their interests in film, in abstract painting, and in the architecture of large structures. Indeed, Pangborn almost visualized them openly sharing the solarium, embarking together on their rejection of the world and the exploration of their absolute selves, their unique time and space.

All the more bitter, therefore, were Pangborn’s reactions when he discovered the intruder’s attempt to kill him.

Too stunned to reach for the telephone and call the police, Pangborn stared at the bottle of sleeping tablets. He listened to the faint breathing somewhere behind him, lower now as if the intruder were holding his breath, waiting for Pangborn’s response.

Ten minutes earlier, while drinking his morning coffee, Pangborn had at first ignored its faintly acrid flavour, presumably some new spice or preservative. But after a few more sips he had almost gagged. Carefully emptying the cup into the wash-basin, he discovered the half-dissolved remains of a dozen plastic capsules.

Pangborn reached into the medicine cabinet and opened the now empty bottle of sleeping tablets. He listened to the faint breathing in the solarium. At some point, while his back was turned, the intruder had slipped the entire contents into his coffee.

He forced himself to vomit into the basin, but still felt queasy when Vera arrived an hour later.

‘You look fed up,’ she told him cheerfully. She nodded at the books scattered around the place. ‘I can see you’ve been reading again.’

‘I’m lending some books to a friend,’ Pangborn reversed his chair away from her as she ambled around the chamber with her valise. Under the seat of his chair he held the handle of a vegetable knife. Looking up at the girl’s overbright make-up and guileless eyes it was hard to believe that she might be in collusion with the intruder. At the same time he was surprised that she could not hear the obvious sounds of the man’s breathing. Once again Pangborn was amazed by his nimbleness, his ability to move from one end of the solarium to the other without leaving more than a few fragments of his presence on the monitor film. He assumed that the man had found a secure hiding place, perhaps in a service shaft unknown to Pangborn.

‘Mr Pangborn! Are you awake?’

With an effort, Pangborn rallied himself. He looked up to find Vera kneeling in front of him. She had pushed back her cap and was shaking his knees. He searched for the knife handle.

‘Mr Pangborn — all those pills in the bathroom. What are they doing?’ Pangborn gestured vaguely. Concerned only to find a weapon, he had forgotten to wash away the capsules.

‘I dropped the bottle in the basin — be careful you don’t cut your hands.’

‘Mr Pangborn -’ Confused, Vera stood up and straightened her cap. She glanced disapprovingly at the huge blow-ups from Psycho on the television screens, and at the blurred fragments of shoulder and elbow recorded by the solarium camera. ‘It’s like a jig-saw. Who is it? You?’

‘Someone else — a friend who’s been visiting me.’

‘I thought so — the place is in a mess. The kitchen… Have you ever thought of getting married, Mr Pangborn?’

He stared at her, aware that she was deliberately being coquettish, trying to unsettle him for his own sake. Once again his skin began to scream.

‘You ought to get out of here more,’ she was telling him sensibly. ‘Visit your friend. Do you want me to come tomorrow? It’s on my route. I can say your aerials need tuning.’

Pangborn reversed around her, keeping an eye on the bathroom and kitchen. Vera hesitated before leaving, searching for an excuse to prolong her stay. Pangborn was certain that this amiable scatter-brain was not an accomplice of the intruder, but if he once divulged the man’s presence, let alone the murder attempt, she would probably panic and then provoke an openly homicidal assault.

Controlling his temper, he waited until she left. But any irritation he felt was soon forgotten when a second attempt was made on his life.

As with the first murder attempt, Pangborn noticed that the method chosen was both devious and clumsy. Whether because he was still half-doped by the sleeping pills, or out of sheer physical bravado, he felt no sense of panic, but only a calm determination to beat the intruder at his own game. A complex duel was taking place between them, its fragmentary course displayed in a lengthening series of giant blow-ups on the screens — his own suspicious hands a few feet from the camera, the intruder’s angular shoulder silhouetted against the kitchen door, even a portion of an ear reflected in the mirror of the medicine cabinet. As Pangborn sat in his chair, comparing sections of this visual jigsaw with the elements from the shower sequence in Psycho, he knew that sooner or later he would assemble a complete picture of the intruder.

Meanwhile, the man’s presence became ever more evident. The smell of his body filled the solarium and stained the towels in the bathroom. He openly helped himself to the food in the refrigerator, scattering shreds of salad on the floor. Tirelessly, Pangborn maintained his round-the-clock surveillance, trying to shake off the effects of the sleeping pills. So determined was he to defeat the intruder that he took for granted that the water in the bathroom tank had been fouled with cleaning soda. Later, in the kitchen, as he bathed his stinging face with mineral water, he could hear the self-satisfied breathing of the intruder, celebrating another small deceit.

Later that night, as he lay half-asleep in front of the television screens, he woke with a start to feel the hot breath of the stranger against his face. Startled, he looked round in the flickering light to find the vegetable knife on the carpet and a small wound on his right knee.