The Keys of Marinus is my first 10/10 story of Classic Who. As with the other stories thus far, we're treated to another very strong first episode - this is the way to begin a story! Mysterious, imaginative, quirky - it does an excellent job of setting the tone, and I particularly loved the proto-Wilhelm scream and the plethora of revolving panels littering the outer wall of the building.

Barbara is my favorite character in season one, and episodes two and three are prime examples why. Here we have traps and puzzles galore! It's all very Temple of Doom, with Barbara coming in strong again and again. Susan even helped rescue everyone! One thing I appreciate in episodes two through four is the focus on the other characters while The Doctor is away. In episode two, we were treated to Barbara and Ian working on their own, and in episode three, it's those two with actual help from Susan, which may be the first time since she navigated the petrified jungle to fetch the medicine in The Daleks. I also appreciate the swift location-hopping in this story and the sense of actual menace from anything and everything around them - acid oceans, sentient vegetation, roving wolves, bitter cold, booby traps.

Hartnell returns from vacation completely energized here, and his performance is excellent. Episode five may showcase some of the first glimmerings of The Doctor as someone who is steps ahead of everyone else. Susan was feisty rather than whiny; Barbara was calm and steady; and Ian was stoic, trusting The Doctor to defend and rescue him from a tight spot. I've awarded individual episodes five stars before this; however, not all five-star episodes are created equal, and this one was truly outstanding. This is quite possibly the best story of Season One. It's at least the most consistent, with none of the episodes appreciably dropping in quality, plus the ending was at once touching and sagacious. All the characters had a chance to shine, and the seeds of what is to come have clearly been sown. And so, we venture into The Temple of (Elemental) Evil...