The Duc de Richleau and Rex van Ryn are horrified to discover that their friend Simon has joined a Devil-worshipping sect presided over by the powerful Mocata. The Duc takes Simon back to his house in a bid to free him of Mocata's influence. Simon is compelled to escape and - together with another novice, Tanith - falls back into Mocata's clutches. Simon and Tanith attend a woodland Black Mass and are prepared for their rebaptism into evil. Mocata summons the Goat of Mendes - the Devil himself - before Rex and the Duc take Simon and Tanith to safety. Mocata's magic is omnipresent, however, and the Duc draws a holy circle on the floor to defend them. As Mocata conjures a giant tarantula, and then the Angel of Death, the forces of darkness threaten to overwhelm them all...

Adapted from the bestselling novel by Dennis Wheatley, The Devil Rides Out contains scenes of Satanism that proved controversial when the film was released in 1968. Now regarded as one of the greatest Hammer horrors, the film is a favourite of leading man Christopher Lee.