Tom Baker (Doctor Who), Matthew Waterhouse (Adric)
Anthony Ainley (Tremas*), Sheila Ruskin (Kassia), Sarah Sutton (Nyssa), Denis Carey (The Keeper) [1-2], John Woodnutt (Seron) [1-2], Margot van der Burgh (Katura), Robin Soans (Luvic), Roland Oliver (Neman), Geoffrey Beevers (Melkur)*, Liam Prendergast , Philip Bloomfield  (Fosters)
||John Nathan Turner
The Union of Traken is governed by a Keeper gifted with the powers of the Source. The current Keeper is nearing the end of his thousand-year tenure, however, and asks The Doctor and Adric — who have escaped from E-Space — to go to Traken and stop an evil he believes is plotting to destroy the Union.
But the source of the evil, the Melkur, has already infiltrated the Consuls of Traken, and has The Doctor declared a criminal. Allying himself with Consul Tremas and his daughter, Nyssa, the Time Lord must uncover the true power behind the Melkur — someone who knows The Doctorof old.
This is the first part in the Return of the Master trilogy, which continues in Logopolis and concludes in Castrovalva.
Nyssa reutrns in the following story, Logopolis, when a shadowy version of the Doctor’s next self saves her before Traken’s destruction.
Adric applies a Fourier analysis on the energy readings from the Melkur
There is some confusion as to what exactly Tremas’s body is to The Master. While it appears that it now houses The Master’s mind, another theory is that its simply superimposed, if you like, over The Master’s corpse, and kept alive by the dying embers of the Source of Traken, as speculated in The Quantum Archangel.
The Fourth Doctor has already met an older version of Nyssa in Asylum.
The Master’s TARDIS is shown to have offensive weaponry, which it uses in its Melkur form, and will again in Castrovalva
Continuing the tradition of the Master having aliases of “Master”, Tremas is an anagram. Geoffrey Beevers is credited as the Melkur to conceal the plot twist of the Master’s return. Even after the identity of the person inside the Melkur has been revealed in part three, the closing titles still credited it Beevers as “Melkur”. The Melkur statue itself was actually played by Graham Cole, who remained uncredited both on-screen and in Radio Times.
The Master is nearing the end of his twelfth regeneration, making him the thirteenth incarnation.
* Anthony Ainley will resume regular appearances as The Master
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