A force grips the TARDIS and transports it back 4.5 billion years to the origins of the Earth. The Doctor and Sarah-Jane explore the ball of gas that exists in a space, before the TARDIS skips millions of years into the future to the more solid, crust-forming planet. As they watch, they suddenly hear the voice of the Megron, "High Lord of Chaos", who claims he now controls the Earth - a planet of chaos and disharmony. The Doctor disputes this, saying it is a sign of progress and the coming order. Thrown further into the future they arrive at an Earth covered in volcanoes, where Sarah finds it all disturbing until the Doctor indicates mountains forming and the beginning of order. The Megron furiously tries to deny the oncoming emergence of a sustainable planet, but as the Doctor counters by showing an Earth now with its own oxygen atmosphere - challenging the Megron to a telepathic duel, the Doctor wins and banishes him from the Earth as chaos changes to balance.