While dabbling in Satanism, Count Karstein resurrects Mircalla Karnstein who initiates him into vampirism. As a rash of deaths afflicts the village, Gustav the head of Puritan group leads his men to seek out and destroy the pestilence. One of his twin nieces has become inflicted with the witchcraft but Gustav's zeal and venom has trapped the innocent Maria, threatening her with a tortuous execution, whilst Frieda remains free to continue her orgy of evil.

UNIT is providing security cover at an experimental drilling project at Eastchester, designed to penetrate the Earth's crust and release a previously untapped source of energy. Soon, however, the drill head starts to leak an oily green liquid that transforms those who touch it into vicious primeval creatures with a craving for heat. The Doctor is accidentally transported "sideways in time" by the partially repaired TARDIS control console into a parallel universe where the drilling project is at a more advanced stage. Thwarted by his friends' ruthless alter egos, he works to save both universes.

The Doctor, Jamie and Zoe return to Earth and become embroiled in the schemes of Tobias Vaughn. They meet up with an old friend, Colonel (now Brigadier) Lethbridge-Stewart, and some old enemies, the Cybermen.

Margaret Ross is an impoverished old woman who lives alone in a seedy apartment and enjoys a rich fantasy life as an heiress. One day she discovers stolen money hidden by her son and believes her fantasy has come true.

Six children are found spread through out the world that not only have enormous intelligence, but identical intelligence and have a strange bond to each other.

The adventures of The Doctor, a time-traveling humanoid alien known as a Time Lord. He explores the universe in his TARDIS, a sentient time-traveling spaceship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Along with a succession of companions, The Doctor faces a variety of foes while working to save civilizations, help ordinary people, and right many wrongs.

The adventures of The Doctor, a time-traveling humanoid alien known as a Time Lord. He explores the universe in his TARDIS, a sentient time-traveling spaceship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Along with a succession of companions, The Doctor faces a variety of foes while working to save civilizations, help ordinary people, and right many wrongs.