Mma Polopetsi stirred the pot of maize meal. “I see,” she said. “It’s nothing illegal, is it?” She remembered her husband’s imprisonment—how could one forget that spell of loneliness and shame?—and she had not been very enthusiastic about the thought that he would engage in detective work, which could so easily go wrong. And yet everything she had heard about Mma Ramotswe had inspired confidence, and she shared her husband’s gratitude to one whom she regarded as the family’s saviour.

Mr Polopetsi hesitated for a moment, but then shook his head. “It is not illegal,” he said. “And the only reason I have not told Mma Ramotswe is that it is a problem which is worrying her. I have found out what is happening and I can fix it. I want it to be a nice surprise for her.”

The surprise, as he called it, had required some planning, and the co-operation of his friend and neighbour David, who had a battered old taxi which he used to ferry office-workers home from a parking place under a tree near the central mall. David owed Mr Polopetsi a favour, going back to an argument which had flared up with other neighbours over the ownership of a goat. Mr Polopetsi had sided with him and helped his side of the case to prevail, and this had cemented the friendship between the two men. So when Mr Polopetsi had asked him to drive him down to Mokolodi and to help him with something that needed doing down there, he readily agreed.

They set off shortly after seven. In town, this was still a busy time, with the traffic quite heavy, but by the time they reached the last lights of Gaborone and the dark shape of Kgale Hill could be made out to their side, it was difficult to imagine that there were people about, not far behind them. There was the occasional car on the Lobatse Road, but nothing very much, and on either side of the road there were just the dark shapes of the acacia trees, caught briefly in their headlights and then lost to the night. Mr Polopetsi had not told David about the precise nature of the errand, but now he did so.

“You don’t have to come with me,” he said. “You just park the car nearby. I’ll do the rest.”

David stared at the road ahead. “I’m not happy about this,” he said. “You didn’t tell me.”

“It is quite safe,” said Mr Polopetsi. “You aren’t superstitious, are you?”

It was a challenge that had to be met. “I am not scared of these things,” said David.