“But surely that is what detection is all about. Logic, and a bit of psychology. If you know logic, you know how things should work; if you know psychology, you should know how people work.”

He smiled, folding his hands across his stomach, as if preparing for a tutorial. As he did so, his gaze was running down Mma Ramotswe’s figure, and she sensed it. She looked back at him, at the folded hands, and the sharp dresser’s tie.

“So, Mma,” he said. “I would like to spend a long time discussing philosophy with you. But I have a meeting soon and I must ask you to tell me what you wanted to talk about. Was it philosophy after all?”

She laughed. “I would not waste your time, Rra. You are a clever man, with many committees in your life. I am just a lady detective. I …”

She saw him tense. The hands unfolded, and moved to the arms of the chair.

“You are a detective?” he asked. The voice was colder now.

She made a self-deprecating gesture. “It is only a small agency. The No. 1 Ladies’ Detective Agency. It is over by Kgale Hill. You may have seen it.”

“I do not go over there,” he said. “I have not heard of you.”

“Well, I wouldn’t expect you to have heard of me, Rra. I am not well-known, unlike you.”

His right hand moved uneasily to the knot of his tie.

“Why do you want to talk to me?” he asked. “Has somebody told you to come and speak to me?”

“No,” she said. “It’s not that.”

She noticed that her answer relaxed him and the arrogance returned.

“Well then?” he said.

“I have come to ask you to talk about something that happened a long time ago. Ten years ago.”

He stared at her. His look was guarded now, and she smelt off him that unmistakable, acrid smell of a person experiencing fear.

“Ten years is a long time. People do not remember.”

“No,” she conceded. “They forget. But there are some things that are not easily forgotten. A mother, for example, will not forget her son.”

As she spoke, his demeanour changed again. He got up from his chair, laughing.

“Oh,” he said. “I see now. That American woman, the one who is always asking questions, is paying you to go round digging up the past again. Will she never give up? Will she never learn?”

“Learn what?” asked Mma Ramotswe.

He was standing at the window, looking out on a group of students on the walkway below.