She felt happy for him. At least, that was what she told herself she felt.

"Great. What is it? Tell me."

"Turbulence," he said. "Turbulence."

THE ZERO-SUM GAME.

Turbulence is John Clearwater's new passion. Hope knows that his old passion, his old love for many years, was Game Theory. He spent four years at Cal Tech working on Game Theory: the theory of rational conflict. John Clearwater has told her a certain amount about the work he did at Cal Tech. He started with two-person games-two-person zero-sum games, as he put it. A zero-sum game is a game where one person's win is necessarily the other person's loss. "Like marriage," Hope said. "Well, no," John said. "Marriage is a non-zero-sum game. And emotions come into play. One person's loss may not necessarily be another person's gain." John told her there was another factor too: he was particularly interested in games of perfect information, where there were no secrets. In these games, be said, there was always an optimum strategy. That was what he was looking for: optimum strategies. Chess is a game of perfect information, so is tick-tack-toe. Games of perfect information can be infinitely complex or comparatively straightforward. The only condition was that there had to be no secrets. Poker isn't a game of perfect information. Poker is a two-person, zero-sum game without perfect information. "Just like marriage," Hope said. He still disagreed.

I was ready, early the next morning, when Ian Vail came by to pick me up. There was a dirt road that took you a mile or so into the heart of the northern area. It saved a lot of time: a fifth to a quarter of my day was spent in commuting to and fro.

As we drove off Vail told me that he had sent two of his field assistants ahead at first light with walkie-talkies to look for the chimps. With a bit of luck, he said, we might be able to cover most if not all of the northern chimp population in a day. I was very much aware of the aftereffects of my encounter with Mallabar the night before. I asked Vail if he had spoken of our trip to anyone. He looked at me, a little surprised.

"No," he said. "Why?"

"Mallabar thinks it wasn't a baby chimp. That body. He says it was a baboon."

"And you don't agree."

"It's not a question of agreeing. I'm right, he's wrong."

Vail made a face. "Look, Hope, maybe you shouldn't tell me any more, you know? Eugene has been extraordinarily...I just don't want to have to take sides."

I smiled to myself: very Ian Vail. "Oh, don't worry," I said. "I'll keep your name out of it. Just a professional disagreement."

"He must have his reasons. I mean, if you're right."

"I am and he has. Though I've no idea what they are."

I sensed Vail's deepening worry: what was he getting into here? To what extent, by aiding me in this way, might he be going counter to his benefactor's wishes?

"It's awkward for me, that's all," he said feebly. "With Roberta and all that."

Roberta Vail. Ian's American wife and Mallabar's amanuensis and uncredited coauthor. Roberta worshiped Mallabar-the term was not too strong-and everyone knew it, even though her adoration was couched in terms of proper professional awe. Perhaps, I thought now, it was Roberta's fervent devotion to Eugene that had made Ian Vail try to kiss me that day.... I realized, also, that Roberta had better not learn of this trip-not because she distrusted her husband (she didn't), but because of its implicit disloyalty to the God Eugene. However, that was one confidence I knew our Ian wouldn't divulge.

We parked the Land-Rover and set off up the path into the low hills that climbed toward the grasslands of the plateau. We were now right in the middle of the Grosso Arvore National Park, an area of approximately one hundred square miles. Our particular territory, where the northern group of chimpanzees were situated, was smaller, a strip of forest and scrub approximately ten miles long and two miles wide. It supported a fluctuating population of between thirty and forty chimpanzees-now reduced somewhat by the migration of my southerners.

About half of the northern chimps had been spotted by one of Vail's assistants, so we were informed over our walkie-talkies. We made good progress. It took us only about half an hour to reach them. I noticed how the going here in the north was far easier; there was little of the thick forest or dense undergrowth that I encountered in the south.

We were lucky to find so many of the chimpanzees together at one site. The reason was that three large dalbergia trees grew here and the flowers were in bud. I counted fourteen chimpanzees sitting amongst the branches, grazing avidly on the small, sweet bud clusters.

Ian pointed. "Two of the pregnant females are here. Look."

Two down. How many to go?...We sat down about sixty yards from the trees and watched the chimps through our binoculars. It was about half past eight in the morning, probably approaching the end of the first feeding session of the day. Already there was a certain amount of calling and excitement. But the chimps were still gorging themselves. Dalbergia buds are a favorite food and the source would only be available for three or four days before they flowered.

I could see through my binoculars that one young female was heavily in estrus. The pink swelling of the skin of her genital area was remarkably large, a protuberance the size of a big cabbage. The male chimps in her tree were growing increasingly excited and aroused. There was much branch-shaking and displaying, calling and shrieking. But the female kept herself at the very extremity of the dalbergia tree, sitting on thin whippy branches that could not possibly bear the weight of another chimp. Chimpanzees often copulate in trees and occasionally a male would advance out toward her as far as he dared, and squat down, showing her his erect penis, shaking leaves and hitting branches in his excitement. But the female appeared to ignore him, and munched on contentedly, cramming her mouth with handful upon handful of sweet yellow dalbergia buds.

But eventually, as if she sensed their collective arousal had reached a peak, and the waiting males had suffered long enough, she climbed down out of the tree. And at once half a dozen males and adolescent males followed her to the ground. The air was loud with calling and hooting.

I saw one big male, with a patch of brown fur on his neck, take up the familiar squatting position near her. His legs were spread wide and I could clearly see his erect penis, thin and sharp, about four inches long, almost lilac against the dark fur of his belly, quivering above his bulging scrotum resting on the ground.

I tapped Ian's elbow. "Is that the alpha male?"

"Yes. N4A."

"Come on. What's his name?"

"We call him Darius."

"And the female?"

"Crispina."

Darius scratched the earth and rapped the ground with his knuckles. He gazed directly, intently, at Crispina, who was half turned away. She raised her lurid rump and backed slowly toward him, looking round from time to time. Darius squatted, almost immobile, swaying very slightly from side to side, the pale tense cone of his penis twitching slightly. He grunted softly as Crispina backed smoothly into his lap.

It was over very quickly. As he thrust, Darius made a harsh grunting noise, and Crispina screamed. After about five or six seconds, and ten thrusts on Darius's part, Crispina leapt away. Darius picked up a bundle of leaves and carefully wiped his penis. But already Crispina had turned away and was presenting her florid rump to another squatting chimp.

I glanced at Vail. He was peering intently through his binoculars. We watched as Crispina copulated with four of the other attendant males. She refused to have anything to do with two of the adolescents, no matter how histrionically they displayed for her. In fact she seemed more interested in Darius, to whom she returned several times, presenting her rump and backing up to him, even, at one stage, hopefully touching his flaccid penis. But he wasn't interested anymore, or wasn't aroused. Then, as if on some covert signal, everything seemed to calm down. Crispina lay on the ground and groomed herself; Darius and the other males climbed back up into the dalbergia trees. Vail put down his binoculars and chuckled.

"Fascinating...she sure knows what she wants, does Crispina," he said, with what looked like an ugly smirk on his lips.

"What do you mean?"

"Nothing..." He was coloring. "I mean it's fascinating to see a dominant female emerge in the group again. It's taken a while. Shall we move on?"

We left the dalbergia trees and retraced our steps about half a mile before taking a path that headed northeast. One of Vail's assistants had spotted another, smaller group of chimpanzees feeding on termites' nests. Something about Vail's last remark nagged at me.

"What do you mean about a dominant female emerging again?"

"Well, it used to be Rita-Mae, you see. Before she went south. Crispina-what went on there-it was just like Rita-Mae."

"The copulations."

"Yes. And favoring certain males. Rejecting others."

"And you think that's significant. There's some kind-" I searched for the right word, "some kind of strategy?"

"Ah-ha. Another person who hasn't read my paper."

"What paper?"

He looked absurdly pleased with himself. "It's a theory I have. You see, it's not the alpha male that gives the group its cohesion, it's a female. A dominant female. It was Rita-Mae that led the group south, not Clovis."

This was all new to me. "How did Mallabar respond?"

"Oh, he doesn't agree. Not at all. He doesn't think the split has anything to do with sex."

As we tramped along the path toward the termite nests, Vail told me more about the article he had written. I didn't listen particularly hard; my thoughts were suddenly back with the dead baby. And Lena. Eventually, to shut him up, I asked if I could see it sometime. He promised to bring it round.

At the termite nests we found Vail's assistant watching a small group of six chimps feeding on the ants. There was a female here who was very pregnant. Vail said that she was one of the two nomads he logged regularly. Neither had been fully integrated into the northern group.

"She's one of the strange attractors," he said.

"Why did you call her that? Strange attractor."

"Just an expression. Before Crispina became sexually popular, it was these ladies that stirred things up. They would breeze into town, as it were. Is it important?"

"I've heard the phrase before, that's all. In another context."

We watched the chimps feed for a while and then returned to the Land-Rover. My head was full of ideas. I asked Vail to run me through his theory once again. He said that the northern group had been stable, socially speaking, because of the presence within it of a strong, sexually popular female-Rita-Mae. When she left, the other younger females could not fill her role and the group began to fragment socially. Other nomadic females were drawn in by the males in an attempt, Vail thought, to find another Rita-Mae. But it wasn't until Crispina started to become popular and favor Darius-who promptly emerged as the alpha male-that the unrest and disruption caused by the schism began to abate.

"But I can see problems ahead," Vail went on. "Two of the other females in the group are pregnant and so is one nomad. Crispina is the only one with a functioning sexual cycle. When she becomes pregnant, God knows what'll happen."

"What does your theory say?"

"I'm afraid that's where it starts to run out of steam."

Vail dropped me off outside my tent. It was midafternoon, hot and silent apart from the metallic burr of the cicadas. Inside my tent it was stifling. The tin roof was theoretically designed to keep it cooler but I could not calculate why it should. I took off my shirt and wiped myself down. Liceu had folded away my freshly washed clothes in a tin trunk. I opened it and chose a white T-shirt. Then I frowned: the trunk had not been locked. This was not for security; the key hung from a string tied to a handle, but I always asked Liceu to lock the trunk to minimize the risk of any bugs or other clothes-eating insects crawling in.

I pulled on my T-shirt. Perhaps he had simply forgotten. I sat down at my desk and looked at the objects on it: the photograph of my parents, of my sister and her children, the stapler, the red tin mug filled with pens, the scissors, the faceted glass paperweight.... I didn't remember leaving the paperweight in exactly that position. Or the scissors. Or maybe I had. Or maybe Liceu had dusted. I opened the desk drawer. There was my field notebook, rubber bands, paper clips, ruler, my black journal. It all seemed undisturbed. Then a gleam of foil caught my eye, sticking out of a curling-cornered old paperback edition of Anna Karenina. I opened the book. They were still there, my three remaining condoms. But I now knew somebody had been through this drawer. I kept the condoms hidden in the middle of that book, tucked in close to the spine. They weren't there to mark my place.

Hauser or Mallabar?...Then I paused. Surely this was getting a little out of hand? I opened my journal: there was my entry, unaltered. The corpse of a two-to three-day-old chimpanzee infant, partially eaten. What did I expect?

I placed my hands palm down on the warm wood of the desk. The death of a baby chimp. The sexual popularity of Crispina. Ian Vail's theory. And now somebody was going discreetly through my possessions. Looking for something, or merely confirming suspicions?

"Hope?"

Ian Vail was outside. I pulled back the tent flap and let him in.

"God, it's hot in here," he said. He seemed slightly edgy. "I'm heading back out again. Brought you this." He handed me a journal. Bulletin of the Australian Primatological Association.

"I didn't know you were a member," I said.

He grinned apologetically. "It was the only place that would take it. I think I told you-Eugene wasn't exactly falling over himself to help me get it published."

I flicked through the journal looking for his article. I found it: "Sexual and social strategies of wild female chimpanzees." I read a few sentences.

"A real page turner," he said. "Once I put it down I could hardly pick it up again." He chuckled weakly at his old joke.

I was looking down at the open pages in my hands, but from the new proximity of his voice I was aware he had moved closer to me. A few seconds dawdled by. I knew what would happen the moment I looked up.

I looked up. He stepped toward me and his hands gripped my shoulders. I turned my face; his lips and nose squashed into my cheek.

"Hope," he said thickly. "Hope."

"Don't, Ian." I pushed him away. "What do I have to say to you? Jesus Christ."

He looked wretched. The blush burning his fair skin, sweat glossy on his forehead. "I've fallen in love with you," he said.

"Oh my God...don't be so, so ridiculous, Ian. For heaven's sake!"

"I can't help it. Today, when...I thought you-"

"Look. This is not going to go anywhere. I told you the last time."

"Hope, just give me-"

"What about Roberta?" I turned the knife. "I like Roberta," I lied. "I like you, but that's all. You're not being fair to any of us."

He had an odd look on his face, as if he had been chewing on some gristle but was too polite to spit it out.

"Please, Ian."

"I'm sorry. I won't...it won't happen again."

He left. I sat down at my desk and thought about him for a while. Then I read his article. It was really quite good.

Roberta Vail was plain and on the plump side. She had wiry, naturally blond hair that she always wore pulled back from her forehead in a firm, clumpy ponytail. She wasn't unattractive, but she had a tired, slack expression to her mouth. She finished her meal and lit a cigarette. She only smoked when Ian was absent.

"Where's Ian?" I asked, as I sat down opposite her with my tray.

"He's not feeling so good. Not hungry."

I commiserated and started my meal.

There was a quality about Roberta that always baffled me. Perhaps it was her closed, inert countenance-what was she thinking? Was she happy or sad? Did it matter? Or perhaps it was simply that air of mystery that is associated with certain couples: a nagging curiosity on the part of the observer as to how they could ever have been attracted to each other in the first instance; a fundamental ignorance of what it was that the one found alluring in the other.... This may be a little unfair, I thought. I could see what might be thought interesting or appealing about Ian Vail, but as for what he saw in Roberta, I was stumped. But then, I reflected, we are always on shaky ground when it comes to understanding one man's meat or another man's poison in the sexual arena. I have been wrong more times than I care to think, and my oldest friend, Meredith, confided in me after my marriage broke up that she had never, ever understood my obsession for John Clearwater. I was amazed-I thought it would be as plain as day to others.

I returned my attention to Roberta, who was telling me about something she had observed at the Artificial Feeding Area. I stopped listening altogether when Mallabar and Ginga came in. There was an attitude in Mallabar's bearing this evening that was unusual. He seemed to be bracing his shoulders square; his eyes-I know this sounds absurd-appeared brighter. He went through into the kitchen area and Ginga joined me and Roberta.

"What's going on?" I said.

"Eugene'll tell you. Have you a cigarette?"

I offered her a Tusker, Roberta a Kool. She chose Roberta's. We both lit up and Roberta went in search of pudding. Ginga turned to me and positioned her body so we could talk confidentially. Ginga had a narrow face with thin lips, prematurely lined and aged from too many years under the African sun. She had unusual eyes-the upper lids seemed heavy, as if she were dying to go to sleep but was making a special effort for you. She spoke good English but with a pronounced accent-Swiss-French, I supposed; she came from Lausanne. She was very thin. I imagined that in the right clothes she would look elegant. I had never seen her in anything but a shirt and trousers. She wore no makeup.

She patted my hand and smiled at me. Ginga liked me, I knew that.

"Hope, Hope, Hope," she said, mock-despairingly. "Why is Eugene so cross with you? He was in a rage the other night."

I shrugged, sighed, and told her a little about the transformation of dead baby chimp into dead baby baboon. It made no sense to her, she said.

"So where's the body?" she demanded.

"It doesn't exist," I said. I inclined my head in Hauser's direction. "He incinerated it."

Ginga made a face. "Well, you know he's been so worried, Eugene," she said. "For the project. There is no money, you know? It's terrible." She reflected a moment, running a hand through her short hair. She took a slow, avid pull on her cigarette, hollowing her cheeks. She exhaled, giving me a half smile, half grimace.

"But I think everything will be fine now."