- Tegan Jovanka: Doctor, why can't you help them?
- The Doctor: Don't you understand? If I did, it would be the end of me as a Time Lord.
- Tegan Jovanka: What do you mean?
- The Doctor: I can only regenerate twelve times. I have already done so four times.
- Tegan Jovanka: So?
- The Doctor: Don't you see? Eight of them; eight of me.
- Tegan Jovanka: They want your remaining regenerations?
- The Doctor: It's the only way to end their mutation.
- Nyssa: Will the mutants really travel through the rest of time?
- The Doctor: I'm afraid so.
- Nyssa: That's terrible.
- The Doctor: Sometimes you have to live with the consequences of your actions.
- The Doctor: I've got to program a temporal deviation to escape the warp ellipse.
- Brigadier Alistair Gordon Lethbridge Stewart: We stuck on this ship?
- The Doctor: I wonder... if I reverse the polarity of the neutron flow...
- Mawdryn: The Doctor chose to immol' himself. Soon he will be a Time Lord no longer. That is his reward for compassion.