He reached for the door lever and flung the door open. She felt the rain come in as he got out of the van, and then he slammed the door closed again. She saw him grappling with the windscreen wipers, which were recalcitrant. But eventually he freed them and they sprang back into operation again, describing their squeaky arcs in the still heavy rain.

When Mr. Polopetsi clambered back into the van his outer clothing was soaked.

“Look at your jacket, Rra,” she said. “You must take it off. Your shirt will be drier underneath.”

Mr. Polopetsi was stoic. “It’s nothing,” he said. “I shall get dry soon. Let’s just go back now.”

Mma Ramotswe felt that she had to insist. She could see that his shirt was damp, but had not been soaked as thoroughly as his jacket. “No,” she said, starting to tug at the neck and shoulders of the jacket. “Come on now, take it off.”

He sighed. “If you insist, Mma Ramotswe. If you insist.”

She smiled and continued to help him wriggle out of the jacket. “It is for your own good, Rra. Women know about these things.”

The jacket was off his shoulders and she gave it a shake, constrained by the small cabin of the van, but enough to get some of the moisture out. As she did so, an envelope fell out of the pocket.

“A letter,” she said. “I hope it is not wet.”

The letter had fallen on her lap, and she picked it up.

“Oh, it has my name on it,” she said. “Look. Mma Ramotswe.”

Mr. Polopetsi had become quite still. She heard his breathing, which sounded strange, as if he had just run up a flight of stairs. She looked down at the letter in her hands. It was definitely addressed to her. She slipped a finger under the flap and opened it.

Fat woman beware! You think that you are Number 1, but you are Number Nothing!

She read the letter in disbelief, in confusion. It was on the same paper as the last one; it was by the same hand. She looked up. Mr. Polopetsi was staring at the letter.

“I found it in the garage. I picked it up and was going to give it to you.”

She looked again at the piece of paper. Outside, it seemed as if the rain had intensified; there was an insistent drumming on the roof of the van. Watery sounds. “Found it?” she asked. “Where?”

He seemed to hesitate for a moment. Then he said, “I found it on one of the oil drums. You know that one by the side. Somebody must have left it there. It is a wicked letter, Mma. It is from some stupid person who doesn’t know what he’s writing.”