The title of the story says it all really. After the runaway success of "The Daleks" in season one, the Green Blobs in Bonded Polycarbide Armour are back. It's the future - some point after 2164 - and the story focuses not on the invasion itself (still a little beyond the budget and capability of 1964) but on a world ruled by the Daleks and their robotised slaves ("Robomen"). It was adapted as Daleks – Invasion Earth: 2150 A.D., the sequel to Dr. Who and the Daleks.