Mr. Polopetsi smiled. “But do people always tell you the truth?”

Mma Ramotswe peered over the top of her steering wheel. “Not always. But then you can tell when they’re telling lies. If you watch people when they talk to you, you can tell.”

Mr. Polopetsi turned to stare at her, and she met his gaze briefly before looking ahead again at the road. He had looked doubtful, and it occurred to her that this was because of what had happened to him. His experience disproved what she said—he knew that people could not always tell the difference between lies and truth. He had been sent to prison because even a judge, who sits all day and listens to people giving conflicting versions of the truth, even such a person could not tell. Perhaps I claim too much, thought Mma Ramotswe; perhaps I cannot really tell.

They drove on and were soon passing through the outskirts of the village, past the small white-painted houses dotted here and there, past a herd boy with a line of nibbling goats, past a sign pointing off to a butchery somewhere out in the bush. Then suddenly Mma Ramotswe applied the brakes and brought the tiny white van to a halt.

“You see that lady?” She pointed to a woman who was sitting in a chair under an acacia tree, just a few yards off the road. Above her, hanging from a branch overhead, but comfortably within reach, was another chair.

“There is a chair in the tree,” observed Mr. Polopetsi. “I wonder why…”

“I’m going to ask that lady,” said Mma Ramotswe. “She is doing nothing, and she looks like a lady who knows things.”

They got out of the van and picked their way across the dusty strip of land that separated them from the woman under her acacia tree.

“Dumela, Mma.”

Greetings exchanged, Mma Ramotswe pointed up at the extra chair hanging on the branch above the woman’s head. “It is strange to see a chair in a tree, Mma.”

The woman looked up, as if seeing the chair for the first time. “Oh, that chair. That is a chair I keep for visitors, Mma. You see, I sell tomatoes here. I have a small stall, but there was a strong wind last week and it blew the stall away. I am sitting here because I have got so used to it.”

“You could make a new stall, Mma,” said Mr. Polopetsi, gazing up at the chair.

“I will do that soon,” said the woman, “but not just yet.” She looked down at her lap, where her hands were folded. “My hands are not ready for work yet. They have been working, working, working. Now it is time for my hands to take a rest.”