"I am worried about one of our young doctors," said Dr Maketsi. "He is called Dr Komoti. He's Nigerian."

"I see."

"I know that some people are suspicious of Nigerians," said Dr Maketsi.

"I believe that there are some people like that," said Mma Ramotswe, catching the doctor's eye and then looking away again quickly, almost guiltily.

Dr Maketsi drank the last of his bush tea and replaced his mug on the table.

"Let me tell you about our Dr Komoti," he said. "Starting from the time he first turned up for interview. It was my job to interview him, in fact, although I must admit that it was rather a formality. We were desperately short of people at the time and needed somebody who would be able to lend a hand in casualty. We can't really be too choosy, you know. Anyway, he seemed to have a reasonable C.V. and he had brought several references with him. He had been working in Nairobi for a few years, and so I telephoned the hospital he was at and they confirmed that he was perfectly all right. So I took him on.

"He started about six months ago. He was pretty busy in casualty. You probably know what it's like in there. Road accidents, fights, the usual Friday evening business. Of coursea lot of the work is just cleaning up, stopping the bleeding, the occasional resuscitation-that sort of thing.

"Everything seemed to be going well, but after Dr Komoti had been there about three weeks the consultant in charge had a word with me. He said that he thought that the new doctor was a bit rusty and that some of the things he did seemeda bit surprising. For example, he had sewed several wounds up quite badly and the stitching had to be redone.

"But sometimes he was really quite good. For example, a couple of weeks ago we had a woman coming in with a tension pneumothorax. That's a pretty serious matter. Air gets into the space round the lungs and makes the lung collapse, like a popped balloon. If this happens, you have to drain the air out as quickly as you can so that the lung can expand again.

"This is quite a tricky job for an inexperienced doctor. You've got to know where to put in the drain. If you get it wrong you could even puncture the heart or do all sorts of other damage. If you don't do it quickly, the patient can die. I almost lost somebody myself with one of these a few years ago. I got quite a fright over it.

"Dr Komoti turned out to be pretty good at this, and he undoubtedly saved this woman's life. The consultant turned up towards the end of the procedure and he let him finish it. He was impressed, and mentioned it to me. But at the same time, this is the same doctor who had failed to spot an obvious case of enlarged spleen the day before."

"He's inconsistent?" said Mma Ramotswe.

"Exactly," said Dr Maketsi. "One day he'll be fine, but the next day he'll come close to killing some unfortunate patient."

Mma Ramotswe thought for a moment, remembering a news item inThe Star. "I was reading the other day about a bogus surgeon in Johannesburg," she said. "He practised for almost ten years and nobody knew that he had no qualifications. Then somebody spotted something by chance and they exposed him."

"It's extraordinary," said Dr Maketsi. "These cases crop up from time to time. And these people often get away with it for a long time-for years sometimes."

"Did you check up on his qualifications?" asked Mma Ramotswe. "It's easy enough to forge documents these days with photocopiers and laser printers-anybody can do it. Maybe he's not a doctor at all. He could have been a hospital porter or something like that."

Dr Maketsi shook his head. "We went through all that," he said. "We checked with his Medical School in Nigeria -that was a battle, I can tell you-and we also checked with the General Medical Council in Britain, where he did a registrar's job for two years. We even obtained a photograph from Nairobi, and it's the same man. So I'm pretty sure that he's exactly who he says he is."

"Couldn't you just test him?" asked Mma Ramotswe. "Couldn't you try to find out how much he knows about medicine by just asking him some tricky questions?"

Dr Maketsi smiled. "I've done that already. I've taken the opportunity to speak to him about one or two difficult cases. On the first occasion he coped quite well, and he gave a fairly good answer. He clearly knew what he was talking about. But on the second occasion, he seemed evasive. He said that he wanted to think about it. This annoyed me, and so I mentioned something about the case we had discussed before.

This took him off his guard, and he just mumbled something inconsequential. It was as if he had forgotten what he'd said to me three days before."

Mma Ramotswe looked up at the ceiling. She knew about forgetfulness. Her poor Daddy had become forgetful at the end and had sometimes barely remembered her. That was understandable in the old, but not in a young doctor. Unless he was ill, of course, and in that case something could have gone wrong with his memory.

"There's nothing wrong with him mentally," said Dr Maketsi, as if predicting her question. "As far as I can tell, that is. This isn't a case of pre-senile dementia or anything like that. What I'm afraid of is drugs. I think that he's possibly abusing drugs and that half the time he's treating patients he's not exactly there."

Dr Maketsi paused. He had delivered his bombshell, and he sat back, as if silenced by the implications of what he had said. This was almost as bad as if they had been allowing an unqualified doctor to practise. If the Minister heard that a doctor was treating patients in the hospital while high on drugs, he might begin to question the closeness of supervision in the hospital.

He imagined the interview. "Now Dr Maketsi, could you not see from the way this man was behaving that he was drugged? Surely you people should be able to spot things like that. If it's obvious enough to me when I walk down the street that somebody has been smokingdagga, then surely it should be obvious enough to somebody like you. Or am I fondly imagining that you people are more perceptive than you really are…"

"I can see why you're worried," said Mma Ramotswe. "But I'm not sure whether I can help. I don't really know my way around the drug scene. That's really a police matter."

Dr Maketsi was dismissive. "Don't talk to me about the police," he said. "They never keep their mouths shut. If I went to them to get this looked into, they'd treat it as a straightforward drugs enquiry. They'd barge in and search his house and then somebody would talk about it. In no time at all word would be all about town that he was a drug addict." He paused, concerned that Mma Ramotswe should understand the subtleties of his dilemma. "And what if he isn't? What if I'm wrong? Then I would have as good as killed his reputation for no reason. He may be incompetent from time to time, but that's no reason for destroying him."

"But if we did find out that he was using drugs," said Mma Ramotswe. "And I'm not sure how we could do this, what then? Would you dismiss him?"

Dr Maketsi shook his head vigorously. "We don't think about drugs in those terms. It isn't a question of good behaviour and bad behaviour. I'd look on it as a medical problem and I'd try to help him. I'd try to sort out the problem."

"But you can't 'sort out' with those people," said Mma Ramotswe. "Smokingdagga is one thing, but using pills and all the rest is another. Show me one reformed drug addict. Just one. Maybe they exist; I've just never seen them."

Dr Maketsi shrugged. "I know they can be very manipulative people," he said. "But some of them get off it. I can show you some figures."

"Well, maybe, maybe not," said Mma Ramotswe. "The point is: what do you want me to do?"

"Find out about him," said Dr Maketsi. "Follow him for a few days. Find out whether he's involved in the drug scene. If he is, find out whether he's supplying others with drugs while you are about it. Because that will be another problem for us.