The doctor glanced at him and then looked away. “We could walk over that way. There is a water tank.” He paused. “We will have rain later on, I think.”

“I think so too,” said Mr. J.L.B. Matekoni. “Your cattle—”

“They are not mine,” the doctor interrupted him. “They belong to my son. He is the one who has cattle. I have never had a cattle post. Nothing like that.”

“You are a doctor. You don’t have time for that. You have more important things to do.”

The doctor nodded. “Maybe. But sometimes the things that doctors do may not seem to be all that important. When I was a doctor up on the mines, most of the time I was giving medicals to men before they were signed on. I had to make them run a mile in the heat and then take their pulse. I looked in their mouths for obvious signs of infection, into their eyes, while all the time, you know, the thing that was going to do the real damage was invisible. No microscope would show you it was there. But it was there. And it was years before we knew what it was and what it would do to our people.” He stopped walking and looked at Mr. J.L.B. Matekoni. “Do you know what I’m talking about, Rra?”

Mr. J.L.B. Matekoni did not meet his eyes. He looked at the ground. “I do.”

They had stopped walking while the doctor spoke; now they resumed. “I lost heart,” said Dr. Mwata. “What could I do? We had the drugs, but could we ever get them to people in time? And then they came and said to me that I was too old to carry on. But I did not want to leave medicine altogether. And so I have found a way of helping, particularly those people who have been told by other doctors that nothing can be done. I take on lost causes, you could say. Like that saint. What do they call him? St. Jude, I think. The Catholics have this saint who will help them when nobody else will.”

They were nearing the water tank, a low-built, half-crumbling concrete construction to which an old lead pipe ran up from the ground.

“Do you think that you can help her?” asked Mr. J.L.B. Matekoni. “Do you?”

They were at the side of the tank. At the edge of the concrete, where it rose up from the sandy soil, a snake had abandoned its old skin, the slough a gossamer tube, twisted by the wind, but still a perfect mould of the creature that had been within. Dr. Mwata reached down and picked it up, delicately holding it so that the sun shone through the crinkle of tiny scales.

“What sort of snake do you think this came from, Mr. Matekoni?”

Mr. J.L.B. Matekoni shook his head. “I cannot tell,” he said.