She shifted in her chair and looked at her watch. It was almost eleven o’clock. The nurses, or some of them, would surely have their tea soon; but not today, perhaps, when they all seemed to be so busy. She closed her eyes for a moment, in comfortable drowsiness, feeling the sun from the window on her face. Eleven o’clock.

The double swing doors at the end of the ward were opened, and a woman in a light green working dress, the uniform of the hospital’s support staff, bent down to put a doorstop in place. Behind her was a floor-polishing machine, a big, ungainly instrument like an over-sized vacuum cleaner. The woman glanced at Mma Ramotswe as she pushed her floor polisher in, and then she bent down and switched it on. There was a loud whining sound as the machine’s circular pad rubbed at the sealed concrete of the floor, and a smell of polish too, from some automatic dispenser attached to the handle. This was a well-run hospital, thought Mma Ramotswe; and a well-run hospital would also be battling against dirt on floors. That was where the invisible enemies were, was it not?—the armies of germs waiting for their chance.

She watched the woman fondly. She was a traditionally built cleaning lady doing an important, but badly paid job. There was no doubt that a number of children would be dependent on that job, on the money that it brought for their food, their school clothes, their hopes for a future. And here was this solid, reliable woman doing her job, as women throughout Botswana would be doing their various jobs at that very moment; her floor polisher whirring, its long electrical cable trailing behind it and out of the door into the corridor.

She was Mma Ramotswe, and she noticed things. She noticed the length of the cable, and all its coils, and she wondered whether there were not places in the ward where the polisher might be plugged in. Surely that would be easier, and would mean that this long cable could not threaten to trip people up in the ward or in the corridor. That would be far more sensible.

She looked about her. The ward was full of plugs, one at the head of each bed. And into each of these plugs there were fitted the lights, the injection pumps, the appliances that helped the patients to breathe…

She rose to her feet. The cleaning woman had now almost drawn level with her and they had exchanged a friendly glance, followed by a smile. She approached the woman, who looked up from her work and raised an eyebrow in enquiry before she bent down and switched off the polisher.

“Dumela, Mma.”

The greeting was exchanged. Then Mma Ramotswe leaned forward and whispered to her urgently. “I must talk to you, Mma. Please can we go outside and talk? I won’t keep you for long.”