Doctor Who: The Fifth Regeneration
Peri: Where is it??
The Fifth Doctor: Where’s what?
Peri: The bat’s milk!
The Fifth Doctor: Finished. Only enough left for one.
Peri: We have to get more!
The Fifth Doctor: Too late Peri. Going soon. Time to say goodbye.
Peri: Don’t give up! You can’t leave me now!
The Fifth Doctor: I might regenerate…I don’t know… [sinks to the ground] Feels different this time…
Story (from “The Caves Of Androzani” and “The Twin Dilemma”):
The TARDIS lands on Androzani Minor, where a dispute has escalated into a full-blown guerilla war between the drug lord Sharaz Jek and the wealthy industrialist Morgus over the drug Spectrox, which can halt the aging process. The Doctor and Peri are exposed to a white fungus in the caves, which is soon discovered to be the unrefined drug known as spectrox toxaemia. Direct exposure is fatal and can only be counter-acted by the milk of the Queen Bat that leaves deep in the caves.