Season 16, 1979, 6 parts, Fourth Doctor (Tom Baker)
The Doctor and Romana land on the planet Atrios and meet Princess Astra, her lover Merak, and The Marshall, the latter of which is war-mad about defeating neighboring planet Zeos in their ages-long war. Secretly Zeos is run by an AI, which is secretly run by a guy in a skull mask (The Shadow – he hates light) who also is secretly advising the Marshall through a black mirror. The Shadow is an agent of the Black Guardian and is hunting for the sixth segment to the Key to Time, which (spoiler) is Princess Astra. K9 is captured by The Shadow and reprogrammed, while Astra is likewise corrupted and transforms herself into the puzzle segment. The Shadow gains entry to the TARDIS while The Doctor is miniaturized by friendly Time Lord Drax (found in the bowels of The Shadow’s space base). The Shadow puts the Time Key together and starts monologuing so The Doctor returns to size, grabs the macguffin and our heroes get away.
The Doctor practically turns to the camera and says the name of the episode out loud, which is always fun. This is the final chapter in the Key of Time story arc which spans the entire 16th season. Overall, a disappointing climax to a fun season. This could easily have been 4 episodes, there’s a lot of chaff in the first 3. It only gets interesting when K9 becomes a servant of The Shadow and The Doctor bumps into Drax. Given how overpowered K9 is as an ally, he should be more of a threat to The Doctor, but he’s defeated easily and stupidly. Also it occurs to me that K9’s eyes are always red, so how can we tell when he’s good or evil? In a rare twist Romana upstages The Doctor when she clues him into the fact that the White Guardian is the evil Black Guardian because he’s unwilling to restore Astra to human form. This leads to the question, was there ever a White Guardian, or was it the Black one all this time?
Maybe we’ll find out in the next episode: Destiny of the Daleks