There's some lovely ideas in this episode. It feels a lot like a Third Doctor/UNIT story (where was UNIT during all of this?), and the foundations for what would become a great show are definitely there. It's just a shame the tone is very uneven, and there is lots of overacting. Also the direction with all the weird camera movements gave me a bit of a headache, and thank goodness one particular character didn't make it to the main series.