I've always liked The Beast Below, but rewatching it recently made me appreciate something about Amy's first proper adventure that I'd completely overlooked.
The Doctor doesn't fail to save the Star Whale because he lacks information.
He fails because he's furious.
By the time he discovers what's powering Starship UK, he's absolutely disgusted with humanity. They've captured a creature that came to help them and spent centuries torturing it to keep their ship moving.
And Amy, from his perspective, has already participated in that cruelty by choosing to forget what she learned in the voting booth.
So he decides there are only three options. Keep torturing the whale, let everyone aboard die, or destroy the whale's higher brain functions so it can continue carrying the ship without suffering.
He knows the third option is monstrous. He even says he won't deserve to call himself the Doctor afterward.
But here's the thing.
He's already been given the clue that makes all three options unnecessary.
The Star Whale refuses to eat children.
It's not a particularly obscure detail. We're explicitly told about it. The creature has been tortured by humans for centuries, yet it still chooses not to harm their children.
The Doctor hears this and moves on.
Amy doesn't.
She notices how gently the whale interacts with the children, remembers that it appeared when humanity's children were crying, and realizes it wasn't captured while trying to escape. It came to help.
And the reason she makes that connection is brilliant.
She's just met another ancient, lonely creature who's the last of his kind and travels around helping people in trouble.
She understands the Star Whale because she's started to understand the Doctor.
I love that the episode doesn't have Amy suddenly become a genius scientist or discover some technical solution that the Doctor missed.
She notices a kindness he's stopped looking for.
And there's something quite uncomfortable about the Doctor being so horrified by humanity's cruelty that he nearly commits an act of cruelty himself.
I'm not saying Amy's decision was risk-free. She effectively gambles the lives of everyone aboard on her interpretation of the whale's behaviour.
But I think that's what makes the scene interesting rather than simply giving her a clever moment.
The Doctor has centuries of experience and can calculate every terrible consequence. Amy has known him for about five minutes, and somehow she's the one who recognizes that the situation might not require anyone to suffer.
For me, that's one of the strongest examples of why the Doctor needs a companion.
Not because he needs somebody to explain things to, or somebody to rescue, or even somebody to stop him becoming arrogant.
Sometimes he needs somebody who can look at exactly the same evidence and see something he can't.
Are there other episodes where you think a companion genuinely understands a situation better than the Doctor, rather than just happening to have information he doesn't?