Years after he changed the landscape of filmmaking with The Exorcist, filmaker and writer William Friedkin moves from fiction to fact with this documentary. What began as a brief conversation between Friedkin and Father Gabrielle Amorth - the head Exorcist for the Diocese of Rome for over 30 years - as two professionals who knew of each other's work, soon transformed into an once-in-a-lifetime opportunity, as Amorth agreed Friedkin could film an exorcism ceremony. It would be the ninth exorcism for a painfully afflicted woman, and it would be filmed by Friedkin alone, with no other crew allowed, no light other than the natural light in the room and a small digital camera-and-mic unit that could capture the ritual and its revelations.
Combining the startling and singular footage from Cristina's exorcism with interviews from priests and psychologists, neurosurgeons and non-believers, Friedkin guides us on a journey into the twilight world between the boundaries of what we know and what we don't.

In the fifth episode of the series, Morgan Freeman sets to examine the nature of evil, visiting a serial killer in prison and witnessing an exorcism in India. He also explores ancient beliefs, including Zoroastrianism.