Mighty still looked worried. “I don’t like to travel on the water at night. It would be dark by the time we came back.”

“Give me a torch,” said Mma Ramotswe. “I shall sit in the front and shine it ahead of us. If there are any hippos, we shall see their eyes in the beam of the torch.”

“You are a brave lady, Mma. Maybe that is why you’re a detective.”

Mma Ramotswe laughed. “I am no braver than anybody else.” Was that true? she wondered. There was Mma Makutsi, after all … “I think that I shall leave my assistant back here. I don’t think that she will want to come.”

WITH MIGHTY’S EXPERT NAVIGATION through the spreading channels of the Delta, it took them barely half an hour to reach Lion’s Tail Camp. It was a more modest camp than Eagle Island, with smaller, tented rooms for the visitors, but still with that stylish old-safari feel that Botswana did so well. The manager was away in Maun, but the head guide, Moripe Moripe, an old friend of Mighty, greeted them warmly and listened attentively to Mma Ramotswe’s story. As her explanation drew to a close, he started to nod encouragingly.

“Yes, Mma,” he said. “I remember that lady. Mma Grant was here at the time. You are right.” He paused, as if fetching something from the dim recesses of memory. “It was July, Mma. I remember it because that was the month that my grandmother became late.”

“Are you sure of that? July?”

He nodded. “Yes, I am.”

She felt the familiar excitement that came with the solving of a mystery. But in this case, although she was pleased to have found out what happened, she felt appalled at what she had done. She had raised the hopes of a man who would now have to be told that the fortune he thought he was going to receive would no longer be his.

She reached into the bag she had brought with her and took out the obituary cutting. “Is this that lady?” she asked.

Moripe Moripe examined the photograph. “That is the lady. She had hair like that. That is her.”

“Are you sure?” asked Mma Ramotswe, looking into his eyes. It seemed unlikely to her that somebody would remember one guest of many, and after a few years had passed.

Moripe Moripe met her gaze. “I am very sure, Mma. If you spend a long time with somebody, and you talk to them a lot, then you remember them.”

Mma Ramotswe skirted round what she thought was a general observation. “Who was the guide who looked after her, Rra?”

Moripe Moripe looked surprised by the question. “But I’ve just told you, Mma. It was me. I was the one. I looked after her for five or six days. That is why I remember her.”