On the eve of May Day, dark elemental forces begin to disturb the village of Devil's End as the Master summons the demon Azal: unexplained murders, a stone gargoyle come to life, and a nigh-impenetrable infernal energy dome. With the Master fully prepared to destroy the Earth, the Doctor and UNIT - aided by a benevolent practitioner of witchcraft - battle the wicked rites of a secret science wielded by an alien from another world.

• BBC
• Jon Pertwee
• Katy Manning
• Nicholas Courtney
• Richard Franklin
• John Levene
• Roger Delgado
• Stephen Thorne
• Stanley Mason