It took the best part of half an hour to reach the farm gate. Once through this, the track improved somewhat, and showed signs of recent use. She noticed the tyre-tracks in the dusty ground and reflected on how a good Kalahari tracker could have told her precisely when the last vehicle had passed by and whether it had been lightly or heavily laden. For those trackers with the necessary knowledge, an antelope or a truck were much the same, both leaving on the earth information about themselves that could be as clearly read as if it were writing on a page.

A farmhouse came into view – a low-slung building with a red tin roof and a long, shady veranda. Behind the house were several outbuildings, including an open-sided garage and a high water-tank made of corrugated iron. A metal windmill of the sort that was common on farms stood beside the tank, its vane sticking out behind it like a pointing finger, its blades turning slowly. The trees themselves were still, but the windmill, being taller, had picked up an invisible breeze, enabling it to pump water into the tank. She stopped the van and got out to stretch her legs. She had not been to this farm before, but the scene seemed both familiar and peaceful. This, she thought, was how you should live, if you possibly could: with your cattle around you, with the land beneath you, with this air about you.

She sniffed at the air. It was pure and dry, and it carried the scent of cattle and dust, and of acacia too – a smell you could never describe, but you took in nonetheless. She listened. There were cicadas somewhere, that shrill note that seemed to fill the sky, and, barely audible, the familiar clanking of the windmill pump. It was a miracle that there was water in such a place, but it was there, deep below; water that came from a long way away but was cool and fresh and pure.

She got back into the van and completed her journey. As she pulled up in front of the house, a door opened and a woman stepped out on to the veranda to peer at the unexpected visitor. Inside the van, Mma Ramotswe composed herself. She felt as she often did before she started an investigation: there was a familiar fluttering of the heart, a feeling of risk, an awareness that she had to be on the lookout for any information that might be presented to her by the body language of the other. It is the first few minutes of any encounter, said Clovis Andersen, that can be most revealing; it is what people do before they have the chance to work out what they should be doing.

The woman came down the couple of steps that led from the veranda. She greeted her visitor courteously, but Mma Ramotswe could sense the curiosity that lay behind the greeting.