Horror of Fang Rock (Fourth Doctor).
A good old fashioned horror story, shape-shifting monster and all. The confined lighthouse set worked to the episode's advantage. The guest cast also did well but I was waiting for both Lord Palmerdale and Adelaide to kick the bucket. I was surprised however that everybody except the Doctor and Leela was killed off. In the beginning I figured at least one would survive to tell the tale.
Yeah. It's hard to really call this one a win when, although they saved the world, all of the guest stars are dead!
Still, I want the Rutans to come back!