'The Ark in Space' (4 Parts) Story Code '4C' by Robert Holmes

The TARDIS materialises on Nerva, a deactivated space station, which is in orbit around the Earth in the far future. The station, nicknamed the Ark, contains the last survivors of the human race, held in suspended animation; the Earth was evacuated thousands of years previously, when solar flares threatened to destroy all life on the planet. A fault in the machinery has prevented the sleepers from being awakened, and so the Doctor repairs the circuits, and the humans begin to revive. He and his friends find the remains of a Wirrn, a giant insect-like creature, which broke into the station and laid its eggs in one of the humans. The eggs hatched, and now the creatures have multiplied, laying eggs in the station's solar stacks. A Wirrn larvae infects the human's leader, Noah, and he slowly begins to mutate into one of the creatures. The time travellers, together with a med-tech named Vira, manage to lure the hatched Wirrn insect creatures into a shuttlecraft, and eject it into space. In a final act of humanity, Noah, now fully transformed into a Wirrn, sacrifices his life to destroy the shuttle and the creatures. The Doctor, Sarah and Harry use the station's transmat system to journey to the planet surface, to check the planet's condition prior to the return of the humans.

Tom Baker (Doctor Who), Elisabeth Sladen (Sarah Jane Smith), Ian Marter (Harry Sullivan); Gladys Spencer, Peter Tuddenham (Voices); Wendy Williams (Vira), Kenton Moore (Noah), Christopher Master (Libri), Richardson Morgan (Rogin), John Gregg (Lycett), Gladys Spencer (High Minister's Voice); Stuart Fell, Nick Hobbs (Wirrn Operators)

Produced by Barry Letts
Directed by Rodney Bennett

TX:
Part 1 - 25th January, 1975 @ 5.35pm - 6.00pm
Part 2 - 1st February, 1975 @ 5.30pm - 5.55pm
Part 3 - 8th February, 1975 @ 5.30pm - 5.55pm
Part 4 - 15th February, 1975 @ 5.30pm - 5.55pm

Notes:
*Featuring the Fourth Doctor, Sarah and Harry

*First appearance of the Wirrn

*Working title for ep 1: 'Puffball'; ep 2: 'Golfball' (in John Luccarotti's original draft - seriously!)