The gymnasium was shrinking. Inch by inch, the walls were moving inwards, encroaching across the periphery of the floor. As they shrank towards each other their features altered: the rows of skylights below the ceiling blurred and faded, the power cable running along the base of the wall merged into the skirting board, the square baffles of the air vents vanished into the grey distemper.

Above, like the undersurface of an enormous lift, the ceiling sank towards the floor.

Gorrell leaned his elbows on the chessboard, face sunk in his hands. He had locked himself in a perpetual check, but he continued to shuttle the pieces in and out of one of the corner squares, now and then gazing into the air for inspiration, while his eyes roved up and down the walls around him.

Somewhere, he knew, Neill was watching him.

He moved, looked up and followed the wall opposite him down to the far corner, alert for the telltale signs of a retractable panel. For some while he had been trying to discover Neill’s spy-hole, but without any success. The walls were blank and featureless; he had twice covered every square foot of the two facing him, and apart from the three doors there appeared to be no fault or aperture of even the most minute size anywhere on their surface.

After a while his left eye began to throb painfully, and he pushed away the chessboard and lay back. Above him a line of fluorescent tubes hung down from the ceiling, mounted in checkered plastic brackets that diffused the light. He was about to comment on his search for the spy-hole to Avery and Lang when he realized that any one of them could conceal a microphone.

He decided to stretch his legs, stood up and sauntered off across the floor. After sitting over the chessboard for half an hour he felt cramped and restless, and would have enjoyed tossing a ball up and down, or flexing his muscles on a rowing machine. But annoyingly no recreational facilities, apart from the three armchairs and the gramophone, had been provided.

He reached the end wall and wandered round, listening for any sound from the adjacent rooms. He was beginning to resent Neill spying on him and the entire keyhole conspiracy, and he noted with relief that it was a quarter past three: in under three hours it would all be over.

The gymnasium closed in. Now less than half its original size, its walls bare and windowless, it was a vast, shrinking box. The sides slid into each other, merging along an abstract hairline, like planes severing in a multi-dimensional flux. Only the clock and a single door remained.

Lang had discovered where the microphone was hidden.

He sat forward in his chair, cracking his knuckles until Gorrell returned, then rose and offered him his seat. Avery was in the other armchair, feet up on the gramophone.

‘Sit down for a bit,’ Lang said. ‘I feel like a stroll.’

Gorrell lowered himself into the chair. ‘I’ll ask Neill if we can have a ping-pong table in here. It should help pass the time and give us some exercise.’

‘A good idea,’ Lang agreed. ‘If we can get the table through the door. I doubt if there’s enough room in here, even if we moved the chairs right up against the wall.’

He walked off across the floor, surreptitiously peering through the orderly room window. The light was on, but there was still no one inside.

He ambled over to the gramophone and paced up and down near it for a few moments. Suddenly he swung round and caught his foot under the flex leading to the wall socket.

The plug fell out on to the floor. Lang left it where it lay, went over and sat down on the arm of Gorrell’s chair.

‘I’ve just disconnected the microphone,’ he confided.

Gorrell looked round carefully. ‘Where was it?’

Lang pointed. ‘Inside the gramophone.’ He laughed softly. ‘I thought I’d pull Neill’s leg. He’ll be wild when he realizes he can’t hear us.’

‘Why do you think it was in the gramophone?’ Gorrell asked.

‘What better place? Besides, it couldn’t be anywhere else. Apart from in there.’ He gestured at the light bowl suspended from the centre of the ceiling. ‘It’s empty except for the two bulbs. The gramophone is the obvious place. I had a feeling it was there, but I wasn’t sure until I noticed we had a gramophone, but no records.’

Gorrell nodded sagely.

Lang moved away, chuckling to himself.

Above the door of Room 69 the clock ticked on at three fifteen.

The motion was accelerating. What had once been the gymnasium was now a small room, seven feet wide, a tight, almost perfect cube. The walls plunged inwards, along colliding diagonals, only a few feet from their final focus…

Avery noticed Gorrell and Lang pacing around his chair. ‘Either of you want to sit down yet?’ he asked.

They shook their heads. Avery rested for a few minutes and then climbed out of the chair and stretched himself.

‘Quarter past three,’ he remarked, pressing his hands against the ceiling. ‘This is getting to be a long night.’

He leaned back to let Gorrell pass him, and then started to follow the others round the narrow space between the armchair and the walls.

‘I don’t know how Neill expects us to stay awake in this hole for twenty-four hours a day,’ he went on. ‘Why haven’t we got a television set in here? Even a radio would be something.’

They sidled round the chair together, Gorrell, followed by Avery, with Lang completing the circle, their shoulders beginning to hunch, their heads down as they watched the floor, their feet falling into the slow, leaden rhythm of the clock.

This, then, was the manhole: a narrow, vertical cubicle, a few feet wide, six deep. Above, a solitary, dusty bulb gleamed down from a steel grille. As if crumbling under the impetus of their own momentum, the surface of the walls had coarsened, the texture was that of stone, streaked and pitted…

Gorrell bent down to loosen one of his shoelaces and Avery bumped into him sharply, knocking his shoulder against the wall.

‘All right?’ he asked, taking Gorrell’s arm. ‘This place is a little overcrowded. I can’t understand why Neill ever put us in here.’

He leaned against the wall, head bowed to prevent it from touching the ceiling, and gazed about thoughtfully.

Lang stood squeezed into the corner next to him, shifting his weight from one foot to the other.

Gorrell squatted down on his heels below them.

‘What’s the time?’ he asked.

‘I’d say about three fifteen,’ Lang offered. ‘More or less.’

‘Lang,’ Avery asked, ‘where’s the ventilator here?’

Lang peered up and down the walls and across the small square of ceiling. ‘There must be one somewhere.’ Gorrell stood up and they shuffled about, examining the floor between their feet.

‘There may be a vent in the light grille,’ Gorrell suggested. He reached up and slipped his fingers through the cage, running them behind the bulb.

‘Nothing there. Odd. I should have thought we’d use the air in here within half an hour.’

‘Easily,’ Avery said. ‘You know, there’s something—’

Just then Lang broke in. He gripped Avery’s elbow.

‘Avery,’ he asked. ‘Tell me. How did we get here?’

‘What do you mean, get here? We’re on Neill’s team.’

Lang cut him off. ‘I know that.’ He pointed at the floor. ‘I mean, in here.’

Gorrell shook his head. ‘Lang, relax. How do you think? Through the door.’

Lang looked squarely at Gorrell, then at Avery.

‘What door?’ he asked calmly.

Gorrell and Avery hesitated, then swung round to look at each wall in turn, scanning it from floor to ceiling. Avery ran his hands over the heavy masonry, then knelt down and felt the floor, digging his fingers at the rough stone slabs. Gorrell crouched beside him, scrabbling at the thin seams of dirt.

Lang backed out of their way into a corner, and watched them impassively. His face was calm and motionless, but in his left temple a single vein fluttered insanely.