He looked puzzled. “Doesn’t she remember roughly where it was? She would have known where the airstrip was in those days. She would have seen the planes. Was it near there?”

“She thinks it was not far from the university,” said Mma Ramotswe. “But she can’t be sure which side of the university. She says that when she drove round the other day everything seemed to have shifted.”

“There are many new roads,” said Charlie. “New roads can make a place look very different.”

“So we start from scratch,” said Mma Ramotswe. “We go down every road. Unless…” She looked at the photograph once more. “Unless there’s something here that we’re missing.”

“You mean some clue, Mma?”

Mma Ramotswe picked up the photograph and scrutinised it. “What have we got? The lady herself? There’s nothing in her clothing that tells us anything.”

Charlie, who had now left his chair to peer over her shoulder, agreed. “Nothing. Just ordinary clothes.”

“And the verandah,” continued Mma Ramotswe. “Nothing there either. Just those fly screens.”

Mma Ramotswe transferred her attention to the small area of yard that appeared in the photograph. There were aloes round the side of the verandah and then, in the background, the spreading branches of a large tree. Such trees were common in gardens in the older parts of town; where new building had been erected, they were sparser.

“What sort of tree is that?” asked Charlie, touching the photograph with a forefinger.

Mma Ramotswe saw that the leaves were just distinguishable. “Jacaranda,” she said.

“There are lots of those,” said Charlie.

Mma Ramotswe sighed. “I’m afraid so,” she said. “So we shall have to start driving round and round.”

“I am very good at that, Mma. I can drive your van for you, if you like.”

Mma Ramotswe hesitated. She normally drove herself, but she knew how much Charlie liked driving. He had no car of his own, of course, and so his only opportunities to drive had come with his work in the garage—now brought to an end for financial reasons—or his work with the agency.

“Will you drive slowly?” she asked. “I know what you young men like to do.”

“I will drive at walking pace, Mma. Slow, slow. We will be overtaken by bicycles.”

Mma Ramotswe laughed. “Perhaps not that slowly,” she said. “All I ask is that you stick to the speed limits.”

“I always do, Mma.”

She looked at him incredulously, but he held her gaze.

“Right, Charlie,” she said, rising from her chair. “Off we go. The investigation begins.”

“And I think it will be over very soon,” said Charlie. “We will find this place, Mma. I have a feeling.”