The orbit of Jupiter, the 25th century. Arriving back on the Nerva Beacon much earlier in history, the Doctor and his friends discover the satellite beset by space plague while its crew struggles to keep space traffic away from Voga, the newest moon of Jupiter. But what is the connection between Voga, the plague, and some old enemies of the Doctor?
Elenco: William Hartnell , Patrick Troughton , Jon Pertwee , Tom Baker , Peter Davison , Colin Baker , Sylvester McCoy .