“This cuff is too small,” he muttered, unwrapping it. “I must get a traditionally built cuff.”

He turned away and opened a cabinet drawer from which he extracted a larger cuff. Connecting this to the instrument, he wound it round Mma Ramotswe’s arm and took the reading. She saw that he noted figures down on a card, but she did not see what he wrote.

Back at the side of the doctor’s desk, Mma Ramotswe listened to what he had to say.

“You seem in reasonable shape,” he said, “for a … for a traditionally built lady. But your blood pressure is a bit on the high side, I’m afraid. It’s one hundred and sixty over ninety. That’s marginally high, and I think that you will need to take some drugs to get it down a bit. I can recommend a very good drug. It is two drugs in one—what we call a beta-blocker and a diuretic. You should take these pills.”

“I will do that,” said Mma Ramotswe. “I will do as you say, Doctor.”

“Good,” said Dr Lubega. “But there is one thing I should tell you, Mma. This very good drug is not cheap. It will cost you two hundred pula a month. I can sell it to you here, but that is what it will cost.”

Mma Ramotswe whistled. “Ow! That is a lot of money just for some little pills.” She paused. “But I really need it, do I?”

“You do,” said Dr Lubega.

“In that case I will take it. I do not have two hundred pula with me, but I do have fifty pula.”

Dr Lubega made a liberal gesture with his hands. “That will get you started. You can come back for some more, once you have the money.”

ARMED WITH HER SMALL BOTTLE of light blue pills, Mma Ramotswe went that evening to the house of her friend Howard Moffat. He and his wife were sitting in their living room when she called at their door. Dr Moffat’s bad-tempered brown dog, of whom Mma Ramotswe had a particular distrust, barked loudly but was silenced by his master and sent to the back of the house.

“I’m sorry about that dog,” said Dr Moffat. “He is not a very friendly dog. I don’t know where we went wrong.”

“Some dogs are just bad,” said Mma Ramotswe. “It is not the fault of the owners. Just like some children are bad when it is not the fault of the parents.”

“Well, maybe my dog will change,” said Dr Moffat. “Maybe he will become kinder as he grows older.”

Mma Ramotswe smiled. “I hope so, Doctor,” she said. “But I have not come here to be unkind about that dog of yours. I have come to ask you a quick favour.”

“I am always happy to do anything for you, Mma Ramotswe,” said Dr Moffat. “You know that.”

“Will you take my blood pressure, then?”