The Keeper of Traken

The Keeper of Traken is the sixth serial of the 18th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 31 January to 21 February 1981.

In the serial, the alien time traveller the Master (Geoffrey Beevers) seeks a power on the planet Traken known as the Source which he wishes to use to restore his life.

In the TARDIS, the Fourth Doctor and Adric arrive back in N-Space following the events of Warriors' Gate in an area known as the Traken Union, an empire of peace and harmony.

The Keeper explains that his title is about to pass on soon to Consul Tremas, giving him access to the powerful Source that is the centre of Traken's technological advancement, but senses evil within him, his wife Kassia, and his daughter Nyssa.

Adric works with Nyssa to identify the energy signature of the plasma as being from a TARDIS, while the Doctor assists Tremas in defusing the conflict over their presence.

Unbeknownst to either group, Kassia secretly visits Melkur, who gives her a collar to wear, providing the creature with mind-control over her while promising to keep her husband safe.

When the Keeper dies, Kassia takes the throne, but as the pivotal moment of the ceremony is completed, she disappears, leaving the statue of Melkur in her place, now connected to the Source.

The producer wanted to include a character that would give a sense of familiarity when Tom Baker, who had been the Doctor for several years, left and the new lead actor took over.