Parts: 4
Writers: Bob Baker, Dave Martin
Airdates: 2 October 1976 - 23 October 1976
Production Code: 4N

Doctor: fourth
Companion: Sarah

Megalomaniac of the Week: Eldrad

Story: As the protective barriers begin to fail around a dome on the planet Kastria, the inhabitants - near dying as cold winds penetrate the structure - monitor the flight path of a capsule containing a despised criminal. Lest the power fail before their task is complete, they decide to detonate the capsule before it reaches its target distance from the solar system...despite the fact that this action might cause part of him to survive the explosion. Their decision reached, the capsule explodes...

And a full 150 million years later, the TARDIS brings the Doctor and Sarah to Earth. Shortly after realizing that they have landed in the middle of a quarry, Sarah hears the sirens blaring - but it is too late, and an explosion flattens both her and the Doctor as dislodged rubble falls. When the Doctor finally finds her, she is holding tightly onto an ancient stone hand. The Doctor takes Sarah to a local hospital, then returns to the quarry to search for clues; meanwhile, Sarah awakens and, armed with a blue ring from the stone hand, steals it from the pathology lab and makes her way to a nearby nuclear reactor. Inside, Sarah manages to breach the core area, where the hand begins to move...

Fed by radiation, the body of a silicon-based lifeform develops from the hand. The creature's name is Eldrad, and she wants the Doctor and Sarah to take her back to her homeworld of Kastria, destroyed years ago by an alien conflict. The Doctor is persuaded to agree...but Eldrad is not as innocuous as she looks, and her plans are far greater than the Doctor knows...