The Doctor (Matt Smith) and Amy Pond (Karen Gillan) bring the TARDIS to the Cabinet War Rooms in London during the Second World War. Winston Churchill (Ian McNeice) is promoting a scientist named Edward Bracewell (Bill Paterson) who has created advanced weaponry for the War Effort, particularly a robotic device he calls Ironsides. The Doctor recognizes it as a Dalek and warns Churchill it is dangerous. There is in fact a Dalek ship in orbit near the moon. Hearing the Doctor, the Daleks aboard activate a Progenitor Device. The Daleks expose Bracewell as an android. The Doctor pursues the Daleks to their ship in the TARDIS, leaving Amy behind.
The Doctor threatens to destroy the Dalek ship, but the Daleks fire an energy beam that lights up London just before an air raid. Five newly designed Daleks emerge from the Progenitor Device. They attack the old Daleks who die willingly. Amy convinces Churchill and Bracewell to use the Daleks’ technical knowhow to modify three Spitfires so they can fly in space. The pilots destroy the disk on the Dalek ship that was firing the energy beam.
Before the Dalek ship is destroyed, Bracewell is triggered. He contains an unstable wormhole that will consume Earth. The Doctor calls off the attack by the last Spitfire and returns to Earth. He helps Amy to convince Bracewell that he is more human than machine, deactivating the wormhole device. The Daleks retreat into hyperspace. The Doctor and Amy remove the advanced tech and convince Bracewell he need not be deactivated since he saved the world.
There are many references to previous Dalek adventures. There is a crack in the wall behind the TARDIS similar to that in Amy’s childhood bedroom. Writer Mark Gatiss visited the replicated Cabinet War Rooms in London. He voiced the Spitfire pilots. The Daleks were in fact based on the Nazis when first created. The episode received mixed reviews, but the new, multicolored Daleks were a hit with children. Nicholas Briggs, as usual, did their voices.
Churchill says, “If Hitler invaded Hell, I would give the Devil a good reference.” That is a somewhat garbled version of something he really said in Parliament. There are eight Daleks on the screen at the same time, a record then. White Daleks are Supremes, Reds are soldiers, Blues are strategists, Oranges are scientists, and Yellows are Eternals. When the script of this episode was written, no-one knew who would be chosen as the new Doctor, so the character was written to be like Jon Pertwee. In actual fact, Jon Pertwee was an intelligence officer during World War II and reported directly to Churchill.