Keys of Marinus is like every stereotypical 60's Who comic that was about 5 pages long was rolled into one 6-parter and put to screen. It has it all; a long-winded quest across various exotic locales, at least one companion being framed for murder, lots of over-the-top screaming from the female companions, lots of action man moments for the male companion - you name it! Sprinkle in a Terry Nation monster that the crew expected to be as big as the Daleks but never quite caught on, and you have perhaps the most quintessentially First Doctor story ever.

And you know what? It was a hell of a lot of fun. It did peter out close to the end with the whole murder mystery plot (what was the killer's motive again?), and the side cast were incredibly underbaked. Also, am I the only one who was surprised at how little the Voord were in this? I was under the impression that they would be following the crew across Marinus as they got the different Keys, but they only pop up in the first and final parts and all get blown up at the end in a slighltly anticlimactic finale. Nonetheless, this is definitely on the upper end of 60s sci-fi stories and I could quite easily see myself watching it again. 8/10.