STORY PLOTLINE
The TARDIS has arrived on a far-distant and seemingly idyllic world, but the Doctor, Steven and Dodo discover that it hides a terrible secret: the apparently civilised Elders maintain their advanced society by draining off and transferring to themselves the life-force of a group of defenceless Savages.
Outraged at this exploitation, the Doctor is seemingly helpless to prevent it when some of his own life-force is tapped by the Elders' leader, Jano.