What is sinister preacher John Laputa doing on a remote Scottish shore in the moonlight hours?Young David Crawfurd and his friends are lucky to escape with their lives when they disturb his rituals.Years later David travels to Africa and meets the minister again, this time in company with the evil Henriques. Using his knowledge of Laputas background David investigates the mystery that surrounds Blaauwildebeestfontein, the Rooirand mountains and the legend of Prester John and discovers a plot, backed by an illicit diamond trade, using the native tribes to take control of Africa and destabilise the continent.Although Buchan has since been accused of political incorrectness he knew the country well and it is interesting to set his observations against the profile of Africa today-particularly in the content of the letter which closes the story.Irrespective of the political ramifications the story is very exciting and is considered one of Buchans' best adventure yarns.