The mysterious Doctor and his granddaughter Susan are joined by unwilling adventurers Ian Chesterton and Barbara Wright in an epic struggle for survival on an alien planet.

In a vast metal city they discover the survivors of a terrible nuclear war - The Daleks. Held Captive in the deepest levels of the city, can the First Doctor and his companions stop the Daleks' plan to totally exterminate their mortal enemies, the peace-loving Thals? More importantly, even if they can escape from the Daleks, will Ian and Barbara ever see their home planet Earth again?