The Kingdom of Darkness argues first that the Devil acts in this world through “daemons, specters, witches, apparitions, possessions, disturbances.” Devil performs “malicious” and “supernatural” deeds. The author, R.B., is arguing against “atheists” who dismiss possession as nothing more than fantasies of the mind or diseases or natural causes.
In the long, second section the author recounts seventy-nine case studies of demonic possession. These case studies are related to R.B. by “credible Historians.” For each case study, R.B. explains how it was clearly the work of the Devil and not simply a disease.
The conclusion reiterates his main point about possession being the work of the Devil. Nobody, not even atheists he claims, can deny the reality of witches and possessed people. And this alone demonstrates the Devil’s actions in the world.