DOCTOR: We should go and investigate. Identify what's disturbing your concentration, Compassion. Prevent you walking into the furniture. Then we can all stop worrying about you.

COMPASSION: I don't care whether or not you worry about me.

DOCTOR: Good. So you won't care if we do something about it.

FITZ: You don't really need me. Why are you waiting for me?

COMPASSION: It's the right thing to do.

FITZ: You're starting to sound like the Doctor.

COMPASSION: You make that sound like an insult.

FITZ: What's the bloody point? You can knock it off with the concerned-friend routine, too. You don't need me. You can find the Doctor without me. Leave me here to rot with Ellis. I can find out if he smells better once he's been dead for a while.

COMPASSION: Of course we need you, Fitz. You don't think the Doctor would leave you here anyway, do you? The Doctor trusts you, he doesn't trust me.

COMPASSION: He likes you, and he needs you. We both do. You can... see the big picture. The Doctor's off at so many tangents. And I think he gets lost in the detail.

COMPASSION: Remember that the Doctor isn't perfect, either.

FITZ: I know that.

COMPASSION: You dote on the Doctor, Fitz. You haven't worked it out yet, how he tolerates us. Humans are just the Time Lords' embarrassing relations. Isn't it how you'd feel if you had to travel round with only the inferior species for company?

FITZ: You make us sound like pets. Is that your big idea, Compassion? We're the Doctor's pets?

COMPASSION: Yes. But it's like the difference between cats and dogs. A dog thinks, My owner loves me and feeds me and takes care of me, so he must be god. A cat thinks, My owner loves me and feeds me and takes care of me so I must be god. He's got you to sit up and beg, like a well-trained dog. Well, he won't change me.

The Doctor slumped on the leather seat, his breath coming in ragged gasps. Fitz stared, unsure what else to say. The hunched shape looked so vulnerable that Fitz wanted to stoop down and hug him until the pain went away, until the shaking stopped and the real Doctor returned.

The Doctor grinned even wider, and noticed that the rubber lips around the robot's speech loudspeaker were doing the same. 'Fascinating. I suppose that's to reduce the common fear that people have of robots, the lack of empathy and expression. You're able to imitate people!'

The robot stood facing him, arms akimbo, its face a picture of mechanical amazement. 'Am I?' it said with a wide-eyed grin. It slapped its forehead again with a tinny clank.

'Yes,' said the Doctor. 'But don't overdo it.'