G is for... Gas Mask Zombies

When a small boy was fatally wounded by a falling bomb during the London Blitz, he was taken to the nearest hospital for treatment. However, it had not been a German bomb which had landed, but an alien spaceship. This was a Chula ambulance craft, filled with nonogenes designed to repair warriors so that they could return to the fighting. The nanogenes used the boy as a template, mistaking his gas mask for part of his anatomy. He was brought back to life with increased strength, and his touch could infect others with the nanogenes - causing them to be copied and to replicate the child. Thus, they too had faces turned into gas mask, and they carried the same injuries he had - such as a scar to the hand and serious crush injuries. Within a short space of time, every doctor, nurse and patient in the hospital was affected. The contagion then began to spread to the wider community, affecting the soldiers tasked with guarding the spacecraft. The boy, Jamie, was compelled to seek out his mother. Psychically linked to him, all the others affected asked for their mother as well. The last person in the hospital to succumb was Dr Constantine. Before transforming, he was able to point the Doctor towards a girl named Nancy, who looked after orphaned children. The Doctor realised that she was not the boy's sister, as she claimed, but his teenage, unwed mother. When the nanogenes came into contact with Nancy they were able to recognise the true genetic pattern for humans, and all those affected were changed back - old injuries such as amputated limbs even being restored.

Appearances: The Empty Child / The Doctor Dances (2005).

• Originally planning to use real WW2 gas masks, the production team found that they were now banned as they were made from asbestos. New ones were created, with baked bean tins used for the respirator section.