Alexander McCall Smith 's books that depict the work of female private detectives in Botswana have been a phenomenal success, selling nine million copies around the world. The agency is, of course, fictional, but in the Zambian capital of Lusaka there's a real-life bureau that employs four female detectives investigating everything from marital infidelity to missing secret service agents. This engaging film follows their work. Producer Dominic Ozanne ; Exec producer Karen O'Connor The African season continues at 8pm on BBC1 as Holby City visits Ghana Africa round-up: page 28