Classic Who S12 • Serial 2 · (4 episodes)
The Ark in Space
The TARDIS lands on a space station orbiting Earth in the distant future. It's seemingly deserted, but the Doctor, Sarah and Harry soon discover that they are not alone. Thousands of humans are in cryogenic sleep, and while they've slept their Ark has been invaded. A parasitic insect race, the Wirrn, have taken control and threaten the very future of mankind.
4 Episodes:
The Doctor's attempt to give Harry a trip in the TARDIS sees the two of them and Sarah Jane arriving onboard a space station in the far future, with some rather deadly security mechanisms.
The Doctor and Harry revive the Ark's medtech, Vira, to help Sarah Jane. But when station commander Noah is revived, he becomes suspicious of the newcomers.
Knowing that Noah has been infected by the Wirrn, the Doctor persuades Vira to halt the reviving of her people, knowing it will place them in danger as well.
The Doctor tries to protect the humans still in cryogenic suspension from the Wirrn, who are determined to use Earth as their new breeding ground.