The blue crystal that the Doctor took from Metebelis III in a previous adventure is desperately sought by the Eight Legs, a race of mutated spiders, as the final element in their plan for universal domination. With help from an old mentor, the Doctor realises the only way to foil the plot is to make the ultimate sacrifice. The Doctor must risk death to return to the cave of the Great One and save the universe.
Jon Pertwee
The Doctor
Tom Baker
The Doctor
Elisabeth Sladen
Sarah Jane Smith
Nicholas Courtney
Brigadier Lethbridge-Stewart
Richard Franklin
Mike Yates
John Levene
Sergeant Benton
John Dearth
Lupton
Carl Forgione
Land
