The Doctor and Amy arrive in the TARDIS at the Cabinet War Rooms during The Blitz of the Second World War, one month after Winston Churchill requested the Doctor's help in the war effort. As the Doctor arrived late, Churchill turned to the scientific advances of Professor Edwin Bracewell, including robotic devices called "Ironsides" but recognized immediately by the Doctor as Daleks. The Doctor tries to understand their purpose in being on Earth at this time, but they continue to act as Bracewell's inventions, ready to serve Britain's war efforts. Angrily, the Doctor attacks the devices, shouting "I am the Doctor and you are the Daleks!" Unbeknown to the Doctor and the humans, a single Dalek ship is in orbit near the moon; upon hearing the Doctor's "testimony", the Dalek aboard uses it to activate a "Progenator Device" and alerts its comrades on Earth. The Daleks reveal their intent and turn hostile, killing several guards and exposing Bracewell as an android before transmatting to their ship. The Doctor follows in the TARDIS, leaving Amy behind for her protection.
The Doctor learns that the ship escaped destruction at the moment of the collapse of the Crucible after it fell through Time by accident, leaving it nearly completely drained of power. The Daleks' objective is to restart the Progenator containing pure Dalek DNA, thus recreating their race. The Doctor feigns to destroy the ship, including himself, before the Progenator completes, but the Daleks fire an energy beam at London that lights up the entire city minutes before an air raid, leaving the Doctor's allies vulnerable and creating a stalemate.
Then, five brand new, more powerful Daleks emerge from the Progenator Chamber. They disintegrate the older "inferior" models who were willing to allow this, knowing that they were not "pure" Dalek. At the same time, Amy convinces Churchill and Bracewell to use the technology know-how they have (from the Daleks) to modify three Spitfires so that they can fly in space. The pilots attack and destroy the dish on the underside of the Dalek ship that was firing the energy beam, saving London before it can be destroyed by German bombers.