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.
Jon Pertwee
Katy Manning
Nicholas Courtney
Richard Franklin
John Levene
Roger Delgado
Stephen Thorne
Stanley Mason
Damaris Hayman
Don McKillop
Rollo Gamble
Robin Wentworth
David Simeon
James Snell
John Joyce
Eric Hillyard
Jon Croft
Christopher Wray
Gerald Taylor
Alec Linstead
John Owens
Matthew Corbett