Having lived through traumatizing events during WWII, Father Lankester Merrin takes a sabbatical from the Church to conduct archaeological excavations in British-administered East Africa. Merrin unearths an ancient Byzantine church believed have been built and then immediately buried to keep down evil from the crypt below. The natives are convinced that uncovering the church has unleashed a demon, and begin to violently clash with the British military troops. As the village rapidly disintegrates into chaos and war, Merrin must face-off with the demon which has taken possession of somebody close to him.
Haunted by terrible acts the Nazis forced him to participate in, the disenchanted Father Lankester Merrin focuses his energies on helping with an archaeological dig in the northern part of Kenya. There, the crew uncovers a church that predates Christian missions into the area, but the discovery also causes strange events to start occurring — including physical changes to a young, disabled boy, whom Merrin grows to suspect has been possessed by a demon.