The TARDIS materializes on an apparently harmonious planet.  The Doctor and his companions discover that the 'civilised' Elders maintain their lifestyle by draining it from the life-force of 'savages'.  The Doctor, trying to right this wrong, has some of his life-force given to the Elders' leader, Jano.  Jano also gets some of the Doctor's beliefs and he rises against the Elders.  He joins with the Savages to destroy the laboratory that syphons off the Savages life-force.  In the end, Steven remains on the planetr to become the new leader of the combined people.