EX01: Doctor Who: Excelis Dawns

Featuring Peter Davison as the Doctor and Katy Manning as Iris Wildthyme, written by Paul Magrs.

That terrible old reprobate and transdimensional adventuress Iris Wildthyme has gone and locked herself up in a nunnery on the savage world of Artaris. Here she is discovered by the Doctor and the reasonably brutal warlord Grayvorn. Together - with a peculiar nun they pick up en route - they must travel the forests and swamps of this ghastly world in Iris's double decker bus in order to tussle - to the death - with a horde of flesh-eating zombies for a mysterious and holy relic of unfathomable value and questionable pedigree.

But what is the Mother Superior's part in all this?

This story takes place during "Frontios."