Any story that has to make its main characters profoundly stupid in order for the plot to work is in pretty bad shape. But if it’s Doctor Who, and it’s the Doctor acting dumb, well, that’s pretty much a deal-breaker.
It’s deeply irritating to have the same Doctor who’s demonstrated such cunning observatory skills over the rest of the season suddenly lose them all and not notice that the most vulnerable of the four humans he’s supposed to be looking after is wandering off. It’s not like four is even a particularly large number to keep track of.
Speaking of which, four people operating the deepest mining operation in human history or something like it? What the hell? As has been said elsewhere, the ‘cheap’ is showing this story. I’d rather wobblier walls and more extras.
OK, back to the Stupid Doctor. Once he gets downstairs with the homo reptilia, he starts hero worshipping one of them because he’s vaguely nice about some things, though he also has a track record of performing dissections on living creatures. Then, later, he starts talking to a woman like she’s the antichrist because she killed someone who was killing her father and had stolen her child. I’m not saying that’s not a bad thing to do; I’m just saying that imprisoning people underground and cutting them open is pretty bad too. I could almost deal with this crazy random moralising by itself, but when you have it in the same episode as the one where the Doctor seems to genuinely believe that the king of the Silurians can start brokering peace with two random humans (of which one will presumably leaving before negotiations can continue), well, he just comes across as a self-righteous, delusional moron.
I don’t like my Doctor like that. I like him idealistic but pragmatic, clever and reserved, observant and intelligent. Until this story, that’s exactly what I thought I was getting. And any episode with Silurians–the original inhabitants of planet Earth–needs more intelligence and moral complexity, not less.
Note: I have no problem with his pathological curiosity getting himself and his friends into mortal danger though. Somehow that just feels right for him. He is a bit of a loon in that regard.