An I.D.B. in South Africa

This fictional book is set in the diamond mining area of South Africa. It begins at a theatre in the area as Major Kildare and Herr Schwatka are seated in a box awaiting the start of the Opera. Major Kildare's attention is drawn to a woman sitting with some companions in the box opposite. He considers her to be very beautiful, but Herr Schwatka tells him that she is of mixed Zulu and European blood and thus unpredictable in nature.