He raised his fork, and then put it down again. It was as if he had been somehow defeated, and there was no point now in eating. “I found out by chance, only by chance. I asked who had been present in the ward just before the third patient went and one of the nurses happened to mention that the cleaner had left the ward just before it happened. She always polished the floor there at the same time on a Friday morning. So I spoke to her and asked her to tell me exactly what she did in the ward.”

Mma Ramotswe encouraged him. She was keen to hear his description of events, and relieved to find out that it tallied with what the cleaner had told her. This meant that he was no longer lying.

“She told me,” Tati Monyena went on. “She told me that she plugged her polisher in near the door. Near the bed by the window. I asked her how she did this and she said that she simply unplugged the plugs that were already in. Just for a few minutes, she said. Just for a few minutes.”

Mma Ramotswe looked down at her mashed potatoes. They were getting cold, and would become hard, but this was no time for such thoughts. “And so she unplugged the ventilator,” she said. “Just long enough for the patient to become late. And then she plugged it back in. But the damage had been done.”

“Yes,” said Tati Monyena, shaking his head with regret. “That machine is not the most modern machine. It has an alarm, which probably sounded, but with the whirring sound of that old floor polisher nobody would hear it. Then, when the nurses checked, they found that the machine was still operating properly, but the patient was gone. It was too late.”

Mma Ramotswe reflected on this. “So did the cleaner know what had happened?”

“She knew that there had been an incident in the ward,” Tati Monyena replied. “But of course she did not know that it had anything to do with her. She…” He stopped. He was looking at Mma Ramotswe with an expression that said only one thing, Please understand.

She picked up her fork and dug it into the potatoes. A little skin had formed on the top, a powdery white skin. “You didn’t want her to know that she had killed somebody, Rra? Is that it?”

His voice was urgent as he replied; urgent, and full of relief that she should understand. “Yes,” he said. “Yes, Mma. Yes. She is a very good woman. She has small children and no husband. The husband is late. You’ll know why. He was ill with that for a long time, Mma, a long time. She herself is on…on treatment. She is one of the best workers we have in the hospital, and you can ask anybody, anybody. They will all say the same.”