At a time in the far-off future, Earth has become uninhabitable. A selection of Humanity is placed, deep-frozen, in a fully automated space station, to await the day of their return to Earth...

Thousands of years later, Doctor Who arrives. He finds things going suspiciously wrong, and the station under attack from the giant Wirrn, deadly creatures who, in their lust for power, now threaten the future of the whole Human Race...

Novelization of the Doctor Who TV series; four episode story "The Ark in Space" (1975), script by Robert Holmes.