Father Merrin (Stellan Skarsgard) is haunted by his experiences in World War II, when occupying Nazi troops forced him to be complicit in their atrocities. In the aftermath, he has renounced his faith and begun working as an archaeologist. He travels to Kenya, where a fifth-century Byzantine church holds ancient relics. There he encounters Sarah (James D'Arcy), a doctor and concentration camp survivor. The strange occurrences that soon begin reunite him with the evil he sought to escape.
