Dancing the Code by Paul Leonard

Dancing the Code is a Doctor Who novel featuring the third Doctor as he builds a machine designed to predict the future. It shows the Brigadier murdering him and Jo in cold blood. Unable to tell where or when this event is destined to occur, the Doctor and Jo decide that they must stay apart.

Jo goes on a top-secret mission to the war ridden Arab nation of Kebiria. But upon arrival, she is arrested and consigned to a brutal prison. The Kebirians have something to hide: deep in the North African desert, an alien infestation is rapidly growing. The Doctor and UNIT soon discover that unless it is stopped, the alien presence will spread to overrun the whole world.