Tegan falls once more under the influence of the Mara and directs the TARDIS to the planet Manussa. There, the Federator's son Lon and his mother Tanha are preparing for a ceremony to celebrate the banishment of the Mara five hundred years earlier. The Mara takes control of Lon and uses him and Tegan to obtain from Ambril, the Director of Historical Research, the 'Great Crystal' - the large blue stone that originally brought it into being by focusing energy from the minds of the planet's one-time inhabitants. The Mara now plans to use the crystal during the ceremony to bring about its return to corporeal existence.
as The Doctor
as Nyssa
as Tegan Jovanka
as Lon
as Tanha
as Ambril
as Dojjen
as Chela
as Dugdale
as Hawker
as Megaphone Man
as Puppeteer
as Fortune Teller
