Stone Town. Larh Thomas Mysteries, #1

An international media company, Mandleson, hires Larh Thomas to investigate embarrassing assets in their archive, as it is about to go public. An embittered ex-employee has stolen a number of paintings by an obscure Victorian painter which went missing in the second world war. He has escaped to Zanzibar, and he is threatening to tell company secrets which go back to the time of slavery on the East African coast.
At first it appears Mandleson are trying to enhance the value of these paintings with a documentary they are making, but then a much darker purpose behind Mandleson's interest in Zanzibar emerges.