The Keeper Arrives in the TARDIS

The Doctor and Adric are visited in the TARDIS by the Keeper of Traken, an elderly wizened man, who is in charge of 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 technology advancement. But The Keeper is concerned as he senses that a great evil has come to his planet in the form of the Melkur, a calcified statue which was once an evil entity, drawn to the goodness and tranquillity of the Union of Traken as a moth is to a flame.

The Melkur arrived years ago on Traken but became calcified in a grove in Traken’s capital. The Melkur has since become something of a holy symbol, and Consul Tremas’ wife, Kassia, has been tasked by talking to it and keeping it clean; that task is soon to be passed on to their daughter Nyssa.

Nyssa and Kassia Argue

The Keeper requests that The Doctor come to Traken to help him prevent the evil from taking control of the bioelectronic Source which is the keystone of the Union’s peaceful society.

When the TARDIS arrives on Traken, The Doctor and Adric visit the Keeper but strangely their presence appears to cause the Keeper to warn the assembled group of a great evil, and though Tremas vouches for them, others, including the Fosters, guardians of the spiritual welfare of the capital, remain cautious about The Doctor and Adric’s presence.

The Doctor Meets Kassia and Tremas

Soon, bodies in the grove are found and The Doctor deduces they have been killed by some type of plasma weapon. While The Doctor assists Tremas in diffusing the conflict over their presence, Adric works with Nyssa and they manage to identify the energy signature of the plasma weapon as being from a TARDIS.

Unbeknown to anyone Kassia, on learning that her husband has been chosen as the next Keeper Nominate which means that she must leave him, secretly visits the Melkur, who whispers to her that he can prevent this. In desperation Kassia agrees and the Melkur gives her a headband to wear – but this gives the creature mind-control over her.

Controlled by the Melkur, Kassia convinces the Fosters to arrest Tremas, The Doctor, Adric and Nyssa. She then uses the situation to convince the other Consuls to install her as the next Keeper. And so when the Keeper dies Kassia takes the throne. But at the pivotal moment of the ceremony, she disappears, leaving the statue of Melkur in her place, now connected to the Source.

Nyssa Tends to the Melkur

It is then that The Doctor discovers that the Melkur is actually the TARDIS belonging to The Master. Inside its operator is still blackened and emaciated as he was in his last meeting with The Doctor (see "The Deadly Assassin").

The Master is on his last regeneration, and seeks to use the Source to give him a new set of regenerations. But The Doctor, with help from Adric and Nyssa, manages to expel him using the Source’s servo shutoff and sanctioning programs causing The Master’s TARDIS to malfunction. When the Melkur disappears Consul Luvic takes the throne, so becoming the new Keeper, and stabilise the Source before it completely dies.

After assuming all is well, and that The Master is no longer on Traken, The Doctor and Adric depart in the TARDIS. But they are unaware that in a last minute ploy The Master traps Consul Tremas, when he discovers The Master’s TARDIS which is disguised as an antique looking longcase clock. The Master then merges with Consul Tremas’ body before fleeing Traken in his TARDIS.

With the death of her mother, and unaware that The Master has taken over Tremas’ body, Nyssa is left wondering as to her father’s whereabouts.