Locked in a Room: Three and Jo are held captive in an Atlantean cell. It leads to one of the most heartwarming stories the Third Doctor ever tells:
The Doctor: Well, the whole of creation is very delicately balanced in cosmic terms, Jo. If the Master opens the floodgates of Kronos' power, all order and all structure will be swept away, and nothing will be left but chaos.
Jo: Makes it seem so pointless really, doesn't it.
The Doctor: I felt like that once when I was young. It was the blackest day of my life.
The Doctor: Ah, well, that's another story. I'll tell you about it one day. The point is, that day was not only my blackest, it was also my best.
Jo: Well, what do you mean?
The Doctor: Well, when I was a little boy, we used to live in a house that was perched halfway up the top of a mountain. And behind our house, there sat under a tree an old man, a hermit, a monk. He'd lived under this tree for half his lifetime, so they said, and he'd learned the secret of life. So, when my black day came, I went and asked him to help me.
Jo: And he told you the secret? Well, what was it?
The Doctor: Well, I'm coming to that, Jo, in my own time. Ah, I'll never forget what it was like up there. All bleak and cold, it was. A few bare rocks with some weeds sprouting from them and some pathetic little patches of sludgy snow. It was just grey. Grey, grey, grey. Well, the tree the old man sat under, that was ancient and twisted and the old man himself was, he was as brittle and as dry as a leaf in the autumn.
Jo: But what did he say?
The Doctor: Nothing, not a word. He just sat there, silently, expressionless, and he listened whilst I poured out my troubles to him. I was too unhappy even for tears, I remember. And when I'd finished, he lifted a skeletal hand and he pointed. Do you know what he pointed at?
The Doctor: A flower. One of those little weeds. Just like a daisy, it was. Well, I looked at it for a moment and suddenly I saw it through his eyes. It was simply glowing with life, like a perfectly cut jewel. And the colours? Well, the colours were deeper and richer than you could possibly imagine. Yes, that was the daisiest daisy I'd ever seen.
Jo: And that was the secret of life? A daisy? Honestly, Doctor.
The Doctor: Yes, I laughed too when I first heard it. So, later, I got up and I ran down that mountain and I found that the rocks weren't grey at all, but they were red, brown and purple and gold. And those pathetic little patches of sludgy snow, they were shining white. Shining white in the sunlight. You still frightened, Jo?
Jo: No, not as much as I was.
The Doctor: That's good. I'm sorry I brought you to Atlantis.
Jo: I'm not.
The Doctor: Thank you.