They were a bit taken aback. Mr. Polopetsi lifted a hand to his mouth, as if he himself had suddenly spoken out of turn; Mma Ramotswe raised an eyebrow, but only just. “I did not know that,” she said. “Perhaps you could tell me about that, Mma.”

The woman drew in her breath. “Oh, there is a lot to say, Mma. There is so much that I hardly know where to begin. She was an ungrateful girl—very ungrateful. That lady and her husband gave that girl everything. They paid big school fees—big like this—for her to go to school. They bought her pretty dresses and everything she wanted. When she was a little girl I remember her with her mouth full of sweeties all the time. Morning, afternoon. All the time.”

“And her teeth,” observed Mma Ramotswe, even as she thought, If I had been allowed to have my mouth full of sweeties all the time, how I would have loved it!

The woman looked blank. “I do not see what that has to do with her teeth, Mma. I have not said anything about her teeth.”

Mr. Polopetsi intervened. “I think that Mma Ramotswe meant that if her mouth was always full of sweeties, then her teeth would have had many holes in them. Like those places where the rock rabbits live. Those places in the rocks where they make their holes.”

The woman stared at Mma Ramotswe. “Why is he talking about rock rabbits now, Mma? Can you tell me?”

Mma Ramotswe exchanged a quick glance with Mr. Polopetsi. He was well meaning, but he did not know that one should try to keep people on track when one was questioning them. Clovis Andersen himself made that point in his chapter on “Getting to the Truth” in The Principles of Private Detection. “Some people,” he wrote, “cannot resist the opportunity to talk about things that have nothing to do with the case. They wander off in all sorts of directions and lose sight of the subject in hand. Don’t fall into the trap of distracting them.”

“I don’t think it matters much, Mma,” she said soothingly. “I expect that he was thinking of something else. Now, why do you think this girl was ungrateful? If her parents were so kind to her, then why was she ungrateful?”