As the creeping instability closes in on her, the TARDIS locks onto the nearest passing spacecraft, and the process of collapse is halted - but there is no sign of Nyssa.

Hoping that she has escaped onto the strangely deserted host liner, the Doctor goes looking for her. Whether or not he finds her, getting back to the TARDIS will be no easy business...
 

Sabotage! The TARDIS is breaking up! Thanks to the combined efforts of the treacherous Turlough and his evil master, the Black Guardian, the Doctor and his companions are in terrible danger. The outside world has begun to break through and Nyssa has disappeared. Can the TARDIS' fail safe mechanism save them all by docking with another ship? Unlikely, when the nearest vessel is a carrier of plague victims destined for the infamous Terminus, the time-bomb planet ticking at the centre of the universe ...

Running time: 99 mins approx.

Produced by John Nathan-Turner
Directed by Mary Ridge

Originally transmitted from 15- 23 February 1983, this four part adventure starring Peter Davidson is the second in the Black Guardian Trilogy which began with Mawdryn Undead.