'But Brooke, don't you ever want to see something other than the bridge? Mountains, forest, a desert? Think of-'

'My friend,' he says heavily, watching a waiter pour him some coffee, 'do you know how many different types of rock the foundations rest upon?' He sounds patient, almost tired. I am going to be lectured, but at least this will give me a chance to eat my devilled kidneys, which have arrived and are cooling.

'No,' I admit.

'I'll tell you,' Brooke says. 'No less than seven major different types, not counting traces of dozens of others. Every type of strata is represented: sedimentary, meta-morphic, and both intrusive and extrusive igneous rocks. There are major deposits of basalt, dolerite, calciferous and carboniferous sandstone, basaltic and trachytic agglomerates, basaltic lavas, tertiary and old red sandstone and considerable amounts of schistose grit, all present in complex folded systems whose histories have yet -'

I can stomach no more rocks. 'You mean,' I say, as his kedgeree arrives (he coats it with a snowstorm of salt and deposits pepper on it like a layer of volcanic ash), 'that the bridge has more than enough to offer the enquiring mind without recourse to anything outside it.'

'Precisely.'

I'd have said it was more like approximately, but never mind. Anyway, there is something beyond the bridge, something I can almost but not quite remember. I seem to possess abstractions, general ideas, for things I could never find on the bridge; glaciers, cathedrals, automobiles ... a nearly endless list. But I can recall nothing specific, no particular images come to mind. I can cope with my single language and with the customs and mores of the bridge (all surely the product of training at some point), but I can remember nothing of my schooling, my upbringing. I am complete in everything but memories. Where other people have the equivalents of encyclopedias and journals, I have ... a pocket dictionary.

'Well, I can't help it, Brooke,' I say. 'There just seem to be so many things one can't talk about here: sex, religion and politics, for a start.'

He pauses, a forkful of kedgeree poised halfway to his mouth. 'Well,' he says uncomfortably, 'there's nothing wrong with ... the first one, if one's married, or the girl has a licence or whatever ... but damn it, Orr,' he puts the fork down again, 'you're always going on about "religion" and "politics"; what exactly do you mean?

He seems to be serious. What have I got myself into? First this and then a session with Dr Joyce to follow. All the same, for the next ten minutes I attempt an explanation for Brooke. He looks increasingly mystified. Finally, once I have finished, he says, 'Hmm. Don't know why you need two words; they sound like the same thing to me.'

I sit back in awe. 'Brooke, you should have been a philosopher.'

'A philo- what?'

'Never mind. Eat your kedgeree.'

A tram takes me to Dr Joyce's bridge-section. The cramped, rattling upper deck is full of workers; they sit on the grubby seats and read newspapers with large print and photographs. They are almost entirely taken up with sport and the results of lotteries. The men are steel workers or welders; their thick working jackets have no outside pockets, and are covered in numerous small burns. The men talk amongst themselves, ignoring me. Occasionally I think I catch a word - are they using a thick dialect of my own tongue? - but the more I listen the less I understand. Really I should have waited for a soft-class tram, but I might have made myself late for my appointment with Dr Joyce, and I do believe in punctuality.

I take an express lift to the level where the good doctor has his offices. Piped music plays, but as ever it sounds to me like a random collection of notes and jumbled, mismatched chords, as though all music on the bridge has been encrypted. I have given up expecting to hear anything I can remember or whistle.

A young lady shares the elevator for most of the way. She is dark and slim, and looks modestly at the floor. Her lashes are long and black and her cheek curves exquisitely. She wears a finely cut suit, with a long skirt and short jacket, and I find myself watching the rise and fall of her breasts under a white silk blouse. She does not look at me as she quits the lift; a faint hint of perfume is all that's left behind.

I concentrate on a photograph on one of the dark-wood panels by the elevator door. The picture is old, sepia-tinted, and shows three of the bridge sections being built. They stand alone, unconnected except through their jagged, uncompleted similarity. Tubes and girders jut out, festooned with scaffolding and heavy-looking steam cranes are dotted about the brown lines of iron; the three incomplete sections look almost hexagonal. There is no date on the photograph.

A smell of paint permeates the doctor's offices. Two workmen in white overalls are carrying a desk in through the doors. The reception area is empty, apart from white sheets which cover the floor, and the desk, which the workmen place in the centre of the room. I look into the doctor's room; it is empty too, more white sheets covering the floor. Dr Joyce's name has been removed from the door's glass panel.

'What's happened?' I ask the workmen. They look at me blankly.

The lift again. My hands are shaking.

Thankfully, the hospital reception desk has not moved. I have to wait while a young couple with a small child are directed down a long corridor by the receptionist, but then it is my turn.

'I'm looking for Dr Joyce's office,' I tell the stern, thick-set woman behind the desk. 'He was in room 3422; I was there just yesterday, but he seems to have been moved.'

'Are you a patient?'

'My name is John Orr.' I let her read the details on my wrist band.

'Just a moment.' She lifts the telephone. I sit on a soft bench in the middle of the reception area, which is surrounded by corridors: they radiate away like spokes from a hub. The shorter corridors lead to the outside of the bridge; soft white curtains blow in a light breeze. The woman at the desk is transferred from one person to another. Finally she puts the phone down. 'Mr Orr, Dr Joyce has been relocated to room 3704.'

She draws a diagram showing the way to the doctor's new office. My chest aches dully for a while, a circular echo of pain.

'Mr Brooke sends his regards.'

Dr Joyce looks up from his notes, blinking through his grey-pink lids. I have told the doctor the dream about the galleons which exchange boarding parties. He listened without comment, nodding occasionally, frowning sometimes, making notes. The silence dragged on. 'Mr ...?' Dr Joyce says, puzzled. His thin silver pencil hangs over the notebook like a tiny dagger.

'Mr Brooke,' I remind him. 'Came from Surgical at about the same time I did. An engineer; he suffers from insomnia. You were treating him.'

'Oh,' Dr Joyce says after a moment. 'Yes. Him.' He bends back to his notes again.

Dr Joyce's new offices are even grander than his previous accommodation. Three levels further up, with increased floor space, the doctor would appear to be continuing his advancement. He now has a private secretary as well as a receptionist. Unhappily, his elevation has not entailed the replacement of the AYM ('My, Mr Orr, you are looking well! How nice to see you; have a seat. Do let me take your coat. Cup of coffee perhaps? Tea?').

The little silver pencil is replaced in the doctor's breast pocket. 'So,' he says, clasping his hands. 'What do you make of this dream, hmm?'

Here we go again. 'Doc,' I say, trusting that this will annoy him for a start, 'I don't have a clue; not really my field. How about you?'