The Edge of Destruction is a wonderful little story. Being just set in the TARDIS and just starring the main team members it could easily get stale but at just 2 parts it doesn't overstay it's welcome. This episode is sort of psychological horror given that there's no tangible villain, just the minds of the characters being messed with. And as a psychological horror it functions very well. As the characters are stuck in the TARDIS there is a sense of claustrophobia; the lighting and music are also used much more effectively to create a sense of atmosphere then you would expect to see in a lot of the Hartnell era.

Where this story shines though is on it's characterisation. The Hartnell era is great because you can watch the active process of the high Gallifreyan mindset get deprogrammed from the Doctor's head by the companions and you see him develop into a more heroic character. This is a great example of this. Barbara gets to tear the Doctor apart here, it's brilliant and Jacqueline Hill performs it so well. The Doctor's character up to this point has been quite sketchy, he tried to kill an innocent man in An Unearthly Child and deceived Ian and Barbara into going into the city in The Daleks. In this story he similarly has moments of deceptiveness and kinda just being a dick but he is called out and at the end of the story comes round and apologises to Barbara showing his growth as a character. It's very clear that this story is a turning point in strengthen the Doctor's relationship to his friends. Hartnell is on fire here. He gets moments of deceptiveness, brashness, whimsy, kindness and a beautifully written monologue, all of which he delivers fantastically. I feel like I a have a tendency to underrate Hartnell because my god... he's just perfect. Overall this is a story that functions as a cool psychological horror as well as a great character piece and turning point for the Doctor. 8/10 / 4 stars.