“Soon we’ll be at our valley,” Ava told me, smiling.

“ Ourvalley?” I asked.

She nodded, looking as pleased as a traveler who was at last making her way home.

“The valley is a good place. Others will come there to share it with us. Plenty of water and grain and good hunting. Everyone is happy in our valley.”

When we finally reached it, nearly a week later, I saw that it was truly a lovely, sheltered Eden.

We stood by the bank of a gently meandering stream that afternoon, looking down across the valley. The stream dropped down in a series of terraced stone steps to the floor of the valley, then made its way along its length and disappeared into the cliffs at the other end. I saw that those cliffs actually formed the base of the big, double-peaked mountain that smoked quietly, far up at the top where snow still lay glittering white under the late springtime sun.

I could see why the clan was so happy to be here. The valley was sunny and green. From its U-shaped cross section I could tell that it had been scooped out by a glacier, probably from the looming mountain, which had now melted away. It was a very snug niche, quite defensible against invaders. The only easy access to the valley was down the stone terracing of the waterfall, the way we were entering. The trail was slippery, but not terribly difficult to get down. On the other sides the valley walls rose fairly steeply to heights of at least several hundred feet.

Our clan was the first to arrive that year. Dal’s people raced down the wet stone terraces, laughing and happy, to the valley floor. Before the day ended they had felled some trees and chased some game. By nightfall they had erected a few primitive huts with mud walls and tree branches and hides for roofs. The huts were dug into the ground, more underground than above it, but to Dal’s people they seemed like palaces.

One note of sadness touched us that night. The boy who had been injured in the hunt sank into a fevered coma. I had thought at first that the gash on his leg would heal soon enough, but it had become infected despite all that Ava could do in the way of poultices and bandages made from leaves. By the time we had reached the valley, the poor youngster could barely walk; his leg was swollen and inflamed. That night he was delirious, burning with fever. Finally he grew quiet and still. His mother sat at his side all night long. At dawn her keening cry told us all that her son was dead.

The clan buried him that afternoon, with Ava leading a ritual that included lining his shallow grave with all the possessions that the lad had accumulated in fourteen summers: a few stone tools, a handful of smooth pebbles, the winter furs that he had still carried with him. Each member of the clan dropped a flower into the grave while his mother stood quietly and watched. Her weathered cheeks were dry; she had finished her crying. Ava told me later that the boy’s father had been killed two years earlier, and the woman — whose name was Mara — had no other living children. She was too old to expect to find a new husband. She would probably not survive the next winter.

I wondered how they would get rid of her, but didn’t have the courage to ask.

The following morning I walked the length of the valley, following the stream that ran through it. The land must have been tilted by an earthquake, because the stream ran in what seemed to me to be a backwards direction: from the end of the valley where we had entered, it splashed down the stone terraces and ran toward the base of the double-peaked mountain. I would have thought that water would flow from the mountain’s snowcap outward, in the opposite direction.

As I walked slowly back toward the collection of mud huts that the clan had built, I saw Ava off among the flowering bushes by the base of the steeply rising valley wall. I angled off my original path and went toward her. I could see that she was gathering herbs and roots for her store of medicines. Little good that they did for Mara’s son, Ava’s cures were all that these people had to counter disease and injury.

“Hello,” I called to her.

She looked up from the foliage she was studying. “What’s the matter?” she called back.

Striding through the knee-high brush, I answered, “Nothing’s wrong. I was walking down by the stream and I saw you here.”

Ava’s smile was more puzzled than welcoming. Apparently the idea of taking a leisurely stroll and stopping off to chat with a friend was not commonplace among these folk.

“You’re gathering herbs for medicines,” I said.

“Yes.” Her smile faded. “I wasn’t able to save Mara’s son. The devil within him was too powerful for me. I must find stronger medicine.”

Twenty thousand years later, I knew, medical researchers would still be hunting along the same trail.

“You did everything that was possible to do,” I said gently.

She eyed me. “You did nothing to help.”

“Me?”

“You are a man of great powers, Orion. Why didn’t you try to help the boy?”

I was shocked. “I… my skills are in hunting, not medicine.”

Those deep gray eyes of hers seemed to see straight through to my soul. “You have great knowledge; you know things that none of us know. I had thought that your knowledge included healing.”

“It doesn’t.” I felt awkward, apologetic. “I’m sorry, but I just don’t have that knowledge.”

She pushed a strand of coppery hair from her face, still looking unconvinced.

“I told you before,” I said, “I’m only a man.”

Ava shook her head. “I don’t believe that. You are different from any man I have ever seen.”

“How am I different?” I spread my arms, as if to show her that I was built the same as anyone else.

“It is not your body,” she said. “I have tested your body; I have taken your seed. You are strong, but your body is not different from Dal’s or other men.”

My blood ran suddenly cold. So our night of lovemaking had not been wild passion on her part, but a carefully considered experiment. Within my mind I heard a self-mocking laugh: She merely wanted to see what you were made of.

“Your difference,” Ava was saying, “is in your spirit, your soul. You know so much more than we do!”

“I know some things, true enough,” I said, trying to ignore the laughter ringing within me. “But there is much that I do not know.”

“Teach me!” she blurted. “Teach me all the things you know!”

That took me by surprise. Suddenly she was eager for knowledge, avid.

“There are so many things I must learn, so many things I don’t know. Teach me. Share your knowledge with me,” she pleaded.

“I can teach you some things, Ava,” I replied. “But much of what I know would make no sense to you. It wouldn’t be useful to you or to the clan.”

“But you will teach me?”

“If you wish.”

“I do!” Her eyes were wide with excitement.

“But why do you want to learn?” I asked.

She stared at me, momentarily speechless. “Why? To know, to understand — that is the important thing. The more I know, the more I can help the clan. If I had known enough about healing, I could have saved Mara’s son.”

It was my turn to fall silent. Beneath her unwashed skin and rude clothes, Ava was as fully human as Marie Curie, and as inquisitive. More than that, she realized that knowledge was the key to power, that understanding the world around her would help her to learn how to manipulate that world to her own ends. But she misinterpreted my silence. Haltingly, she said, “There is nothing I can give you in return for your knowledge…”

So the idea of trading sex for power had not occurred to her. I almost smiled at the realization that the world’s oldest profession had not yet been invented.

“There are things you know that I don’t,” I replied. “We will exchange knowledge for knowledge. Fair enough?”

“Yes!” She was almost breathless with enthusiasm.