BBC Radio 4's dramatisation of The Exorcist

THE AUDIO DRAMA WAS BROADCAST on two consecutive nights in February 2014. It was promised to be just as scary as the 1971 horror novel's film adaptation that caused widespread controversy in America and Britain when it was first released in 1973.

As readers already know, the story is about a young girl named Regan and her possession by a demon. Her mother asks Father Karras to perform an exorcism, but he is in a crisis of faith, tormented by his failure to fully devote to the Church and to care for his ailing mother.

In the story, when the exorcism is performed, it is led by Father Merrin – a senior priest who has perviously performed the ritual in Africa – with Father Karras's assistance.

As is often the case, various differences are found between the novel and its film adaptation. To start with, the audio drama focuses on telling a good story using only words and sounds.

Without the aid of a narrator, the listener relies on a clever combination of dialogues and background noises to understand the characters and their journeys, as well as how they interact with each other while responding to specific aspects of their surroundings.

This allows the listener to immerse themselves in the story and experience the plot as it unfolds. We hear Father Karras's emotional turmoil, which makes Regan's sweet, innocent voice particularly soothing.

Hence it is both shocking and confronting when we hear the demon's voice – not just the sort of raspy, croaky gibberish that one might expect, but predominantly a sickeningly syrupy spiel with cadence of speech and a precocity that belies the girl's age. The eerie voice is alluring and offensive at once, at times sharp and threatening but more than often pervasive and persuasive.

The other exceptional part of the audio drama is the final confrontation between the demon and Fathers Merrin and Karras. The whole segment sounds unnervingly chaotic, as it should be, but the impressive psychological battle between the two sides sheds considerable light on Karras's doubts.

At one stage, Father Karras asks: “A village in Nigeria. A 12-year-old girl in Georgetown. Why? What's the purpose of it?” Father Merrin's response to this question is the true gem of the audio drama, which is perhaps also the major message of Blatty's book.