The "Doctor" (Tom Baker) and his new pal "Adric" (Matthew Waterhouse) are parked above the planet of "Traken" when it's throned and elderly keeper visits them in the TARDIS. He's a bit of a harbinger of doom, but still asks the time lord to come to the planet to help avert a bit of nastiness with the statuesque "Melkur". No sooner have they arrived, though, then they are suspected by the locals of being the epitome of evil, and it's clear that the scheming of "Melkur" is already well under way - and that he has a fifth columnists from amongst the hierarchy of councillors to help with his devious plan. As this four-part adventure continues, we see that the "Doctor" is going to have to come face-to-face with a rather decrepit version of his oldest nemesis for quite a duel of wits. I liked Waterhouse as an assistant. He brought a bit of science and different kind of enthusiasm to the role, and here he works well with Baker and a solid collection of character actors to deliver a simple story that is light on visual effects but actually quite menacing as it races to it's inconclusive conclusion. Not the best nor the most memorable, but still watchable.