The two white men were Belgian mercenaries. They were unusually solicitous because behind them with the main unit of the federal army my real savior was waiting, a man called Mr. Doblin, an officious second secretary from the Norwegian consulate. (The Norwegians were responsible for the interests of British subjects in the country, there being no British charge d'affaires.) Mallabar had helped too. There was a five-thousand-dollar reward for anyone who rescued us.

Half of this had already been claimed by a lucky staff captain. Ian had evaded his pursuers comparatively easily. He had hidden up for the rest of the night and most of the next day before making his way back to the mission school to discover it had been taken over as a federal army battalion HQ.

I learned all this from Mr. Doblin. By the time I had been driven to the nearest airstrip and flown south to the city, Ian was already back at Grosso Arvore, reunited with Roberta. Mr. Doblin was in his twenties, possibly younger than me. He was dark and overweight and in an almost continually pent-up mood of exhilaration over his part in our successful rescue. He complimented me on my composure. Mr. Vail, he said, had been in very bad shape.

"I think he was absolutely conwinced you were dead," he confided. "We have to tell him you are safe at once." I agreed. I left it to Mr. Doblin to communicate the good news to Grosso Arvore.

We flew south in a small, high-winged transport plane with fixed, splayed wheels-a Beaver or a Bulldog or some such name-accompanied by eight surly wounded soldiers from the federal army who had been unceremoniously loaded on board like so many rolls of carpet. I asked Mr. Doblin why they were so fractious and why nobody on board bothered to tend to them.

"They are self-victims," he said. "They all shot themselves," he told me, in a soft discreet voice, just audible above the noise of the engines. "They are flying home to their execution."

In an hour or so the plane banked over the town. I looked out of the window at the clustered spread of tin roofs, like a massive cubist collage, all grays and browns. I watched the ground approach and more details emerge as the plane, following the giant sweep of the river, slowly descended to the airport.

We touched down, and as we taxied we passed the line of Migs parked on their apron. I thought at once of Usman, but I did not experience quite the same jolt of anticipation I expected. I was still tired and numbed by my ordeal, I decided.

We were not dropped at the airport buildings, but taxied round to a wooden hut on the airport perimeter, where the wounded men were delivered over to the airport police. Mr. Doblin and I were obliged to tramp back through the afternoon heat to the arrivals hall. It was only when I stepped inside and saw a kiosk selling beer, soft drinks and magazines that I realized that I had nothing: no passport, no money, no possessions other than the clothes I was wearing.

Mr. Doblin reassured me. A British passport would be provided very shortly. In the meantime he gave me a generous amount of money for which I had to sign an official-looking receipt. He told me a room had been booked at the Airport Hotel and all the necessary authorities had been informed of my rescue. There was talk of some British journalists flying out to interview me, but he doubted they would be issued visas.

"Stay at the hotel for a few days," he advised kindly. "Wait for your documentation. Relax, eat, swim, enyoy." He covered his mouth with a hand and mumbled conspiratorially, "The British government will be sent the bill." He saw me into a taxi and said he would call at the hotel in a couple of days. It was clear to me that he had not had such fun in ages.

Nothing had changed at the hotel. There was no reason on earth why it should have, but I was vaguely disappointed. When you yourself have suffered considerably, it is hard to cope with the rest of the world's indifference to your experience, and upsetting to see how unmarked it is. You cannot understand its relentless preoccupation with the mundane.

I collected the key to my room. I had cleaned myself up a little since my rescue, but I needed a bath and some new clothes. But now I wanted to see Usman.

I walked through the hotel gardens, and along the concrete pathways toward his bungalow with a new feeling of benign resignation beginning to suffuse me. Mr. Doblin was right: I needed a few days of total, selfish inactivity.

I knocked on Usman's door but there was no reply. I peered through the window and saw his clothes and possessions were still there. Surprises never work for me: the people are never there; the hidden presents are discovered prematurely; the accomplices speak out of turn; the flowers are delivered to the wrong address. I thought I would leave him a note in any event. "Guess who?" I would write and leave my room number; that would at least be a low-order surprise.

An obliging chambermaid opened his door for me. I entered. I smelled his smell. The room was dark and I crossed to the desk to switch on the lamp. As I did so I trod on something that gave with a small satisfying crunch-like standing on stubble in a field, or on a walnut shell. I stepped back and trod on something similar. I returned to the door and switched on the ceiling light.

On the floor were half a dozen of Usman's tiny horsefly airplanes. Two had been crushed-pulverized absolutely-by me. They other four lay where they had fallen. I picked one up. The horsefly was dessicated, a husk, its legs bent, clenched. I picked up the others and laid them carefully on Usman's desk. There was no point in leaving a note.

At the airport I waited in an empty room at the gatehouse. There was stricter security than there used to be-no one was allowed near the hangar where the Migs were parked. Something had changed, at any rate.

I waited for nearly an hour and smoked three cigarettes before someone arrived. Eventually, an immaculate air force officer came to see me. He had pale brown skin and his eyes were small and deeply set. I told him I was a close friend of Usman Shoukry and I wondered where he was. The officer informed me immediately and matter-of-factly: Usman Shoukry did not return from a mission.

I suppose it was news I was expecting, but for some reason I blushed. My eyeballs felt hot in their sockets.

"What happened?"

He shrugged. "A navaid failure, I believe."

"Navaid." I remembered what Usman had told me: your ground crew is your greatest enemy.

"Can I talk to the other pilots?" I asked. I tried to remember their names.

"There are no other pilots." His face slowly formed an expression of vague disconsolation, then brightened. "Can you borrow me a cigarette?"

"Of course." I handed him the pack, he selected one and passed it back to me. We both lit up. "Where are the other pilots?" I asked.

"All the other pilots left, after Usman Shoukry never returned." He looked serious. "Too many navaid failures, they said." He spread his hands. "You see, we have yet to lose an aircraft to enemy fire. And yet we have lost seven, no eight, to navaid failures. And other misfortunes."

"What do you mean?"

"One aircraft was stolen. Two others were damaged in a parking accident."

I exhaled and looked around. I was beginning to feel weak again.

"A navaid failure...could he have crash-landed somewhere?"

"I suppose so." He paused and thought. "In theory." He picked a shred of tobacco off his tongue and looked unfavorably at the burning tip of his cigarette.

"Is this American?"

"No. Tusker."

"What's that?"

"It's a local brand. Don't you know it?"

"I only smoke foreign brands.... Do you like it?"

"Yes."

"My God."

"Have you any idea where his plane might have come down?"

"No. He was far in the north, on the UNAMO front."

"Ah."

"Nobody saw him." He thought again. "He may have crash-landed, but we have no aircraft for a search." He smiled regretfully at me, then, seeing my sad face, said, "Who can say? Maybe he will make his own way home. One day."

TWO KINDS OF CATASTROPHE.

Catastrophe theory is the one we have been waiting for, the study of abrupt change, the catalog of discontinuity. It tells us that all the myriad disasters, downfalls, cataclysms and calamities, great and small, from the unbearably tragic to the mildly irritating, derive from seven basic archetypes of catastrophe.

There are seven types of catastrophe. All forms of abrupt, noncontinuous change will be covered by one or another of these archetypes. They are known as fold, cusp, swallowtail and butterfly catastrophes. There are three varieties of swallowtail, two of butterfly. But the two we are interested in are fold and cusp catastrophes: they are far and away the most common.

Take one easy example of abrupt change in the world-the popping of a balloon. When a balloon bursts there is no way it can be unburst, as it were. The fold catastrophe is like this, conditioned by a single factor. It is the most simple paradigm of change. The balloon bursts, the catastrophe has occurred. There is no going back.

Life is a fold catastrophe, and its single control factor is time. The catastrophe takes place when time stops. In the language of catastrophe theory, our life follows the same mathematical pattern as the inflating and bursting of a balloon. Fold catastrophes cannot be reversed.

Cusp catastrophes are different. In a cusp catastrophe there is always the chance of recovery, a possibility of return to the precatastrophic state. Being knocked unconscious would qualify as a cusp catastrophe; so would a nervous breakdown or an epileptic fit, or boiling a kettle of water.

Take a look at anyone's life. Take a look at your own. In the long fold catastrophe that makes up your three-score years and ten you will encounter many cusp catastrophes along the way.

Hope slept badly on the sofa. Before dawn she managed an hour or two of sounder sleep, but when she woke she felt unsettled and had a persistent dull ache in the small of her back. She drank strong tea and ate a thick slice of toast and Marmite in the kitchen, trying to stem the sensations of nervy irritability that made her feel oddly tense and jumpy. What was wrong with her? Perhaps it was merely the effects of waking with a sore back after a night of shallow, fitful sleep. Perhaps it was the thin drizzle falling outside that heralded a damp and uncomfortable day in the woods.... Perhaps it was having her estranged husband at home again, sleeping upstairs in her warm bed.

She drove to Knap House along splashy lanes. The clouds were low, dense and formless, and the light that filtered through them was pale and unflattering. In her rearview mirror her face looked lumpy and bloodless. She parked her car in the courtyard of the stable block and tramped up the wooden steps to the project office.

"You feeling all right?" Munro asked, solicitously. "Look a bit wan."

"I didn't sleep very well. I-" She made her tone more brisk. "I thought you should know that John's here again. Staying with me for a few days."

"Oh. Good." Munro's mild polite smile said: how is he?

"He's much better. I thought, you know, if he met up with those estate workers..."

"I'll make sure everyone knows."

"He'll be going for walks, et cetera."

The office was overheated and overlit. Hope felt a soporific wave wash over her. She wanted to lie down on the wooden floor and sleep.

"Have you thought about the job?" Munro asked, cautiously. "I mean..." He did not elucidate what he meant: it was a coded, timid apology for his presumption in asking.

Hope had in fact hardly considered his offer at all, but she said at once, "Yes. Yes, I have. I'd like to take it on."

Munro's glee was touching.

"Wonderful," he said. "Well...well, that brightens up a dull day." He went on with his genteel compliments, telling her how pleased he was, but Hope barely listened. Instead, she was asking herself why she had spontaneously committed herself to staying on at Knap right through the next summer. There was only one explanation.

She spent a few hours working doggedly in the sodden wood she was classifying. The rain had thickened and the whole world she moved in seemed a succession of variations on water: earth and water, trees and water, air and water. As the afternoon grew murkier she decided to head for home. She had paperwork to do there. Perhaps she would even have an early night. But then she remembered her bed was occupied.

She parked the car outside the cottage. Light glowed from all the windows and she could hear the noise of music from her stereo. She walked round to the back door where she stripped off her heavy, wet parka and waterproof trousers and kicked off her rubber boots.

"Hi, I'm back," she called, as cheerfully as she could manage.

The small kitchen was a shambles. Plates and saucepans were stacked in the sink. An open, empty tin of tuna fish stood on the breadboard beside a crudely cut loaf.

The sitting room was blurry with cigarette smoke. John sat at the table, which was heaped with his books and papers. On one arm of the sofa was a balanced plate with a few shreds of pasta drying on it. A half-empty bottle of red wine stood at John's elbow. He rose to his feet when she came in and crossed the room to kiss her.

"You look freezing," he said, sweeping a newspaper off an armchair, which he ran up to the fire. She sat down in it obediently, feeling her anger pinch her nostrils.

"Great day," he said. "Brilliant."

"What?"

"Work. Like a house on fire. Glass of wine?"

"I thought you weren't meant to drink when you were taking that stuff. Lithium."

"Glass or two won't hurt. Mmm?"

"Just a splash." She took the glass from him.

"Yeah, brilliant," he said again as if he could hardly believe himself.

"What're you doing?"

"Topology. Mainly. Tiling. Very interesting."

"What...what did you do for lunch?"

"Whipped up my tuna, cheese and spaghetti thing. Finished the lot, I'm afraid. I was starving."

Hope threw the last log in the basket on the fire. She sipped the wine, distastefully. She was not keen for it-it was the wrong time of day-but she thought it might help to calm her a little. She needed to banish all her selfish, petty irritations-the mess, the food, the colonization of her space-before she talked to him.

"I spoke to Munro today."

"Who's he?"

She explained. She explained about the extension to her job, the new work required on the water-meadows and the downland.

"What did you say to him?" John asked.

"I said yes."

He thought about it for a second, nodding. "Fine. Good idea. I'd forgotten how much I liked it down here."

"John, you don't understand!"

"Easy...Christ." He looked hurt.

She sat down. "You've got to go," she said simply, flatly. "You can't stay here."

He looked at her. Now he had a bright, surprised expression on his face. She noticed that there were small deposits of dried saliva at the corners of his mouth, small sticky drifts at the junction of his lips. Lithium did that, she remembered.

"I'm sorry," she said.

He spread his arms. "Look, Hope, I understand," he began. "Don't worry. I was just..." He turned and gestured at the papers covering his desk. My desk, she corrected herself.

"I'm sorry, Johnny," she said again. "There's no point in being dishonest about it."

"I'll get all this packed away."

"Christ, there's no hurry. I just had to tell you, that's all. It had to be said. That was the problem. Stay on for a couple of days. Three. Whatever you feel like. We just have to know where we are."

"I might-if you don't mind. Stay on. Just a day or so. I don't feel quite ready for London."

"No problem." She smiled. "I just couldn't carry on just blandly assuming-"

"No. No, sure. You're right." He forced a smile. "I'm bloody sad." He gave a short, dry laugh. "But you're right."

She stood up and came over to him. She put her hand on his shoulder and he leaned his head against her forearm for a second or two. She refilled their glasses with wine. She felt a giant relief spread through her.