The Doctor is called to London War Room by Sir Winston Churchill, the British Prime Minister at the time of the Second World War. He wants to show The Doctor that he's got a new weapon that will help the Allies win the war against the Germans. When the weapon is revealed, the Doctor is none too pleased. The weapon is a Dalek. Sir Winston tells the Doctor that the Dalek was developed by Prof. Bracewell.
The Dalek keeps telling the Doctor that he's here to help the war effort but the Doctor doesn't believe him. The Doctor tries to antagonise the Dalek but keeps failing everytime until the Doctor kicks the Dalek and the Dalek turns. The Dalek had been trying to get the Doctor's voice to open a portal for new Doctors to come. Once The Daleks have got the voice that they needed, they return to their spaceship on the other side of the moon.
The Doctor uses the TARDIS to get to the Dalek spaceship, leaving Amy Pond with Sir Winston. Onboard the Dalek ship, the Daleks are opening a portal for more Daleks. When the portal is opened, the newer, coloured Daleks destroy the older war-coloured Daleks. The Doctor uses a Jammie Dodger biscuit to fool the Daleks into not killing him.
On the ground, Amy persuades the Military to update the spitfires to fly into space to attack the Dalek spaceship which they do. The Daleks order the Doctor to call off the attack otherwise they will blow up Prof. Bracewell as he is a living bomb. With relunctance, the Doctor calls off the spitfire and returns to the War Room. The Doctor returns to the War Room and confronts Bracewell, telling him to disarm which he does after some persuasion. The Dalek spaceship heads off into space.