Professor Bernice Summerfield and the Plague Herds of Excelis

In 2002, The Plague Herds of Excelis was released by Big Finish Productions.

Cover blurb
The once proud city of Excelis is a crumbling ruin in a state of siege, as barbarians catapult pestilent animal corpses into the city to spread disease among those trapped inside. Excelis is a city clinging to life by a thread. But ancient prophecies foretell a final retribution for the past arrogance of its rulers. When the sun is eaten away from the sky, when the ancient relic of Excelis is taken from its rightful resting-place, and when strangers are discovered among the people, then shall the whole world be doomed to die. Today, the sun is a moth-eaten shadow. Plans are afoot to steal the relic. And a very tired and very fraught Professor Bernice Summerfield just stomped into town in the company of a mysterious traveller in space and time known only as Iris Wildthyme. Pitted against a sinister prophet, the machinations of the Imperial court, and hordes of animal undead, Benny finds herself embroiled in the final stages of an aeons-old plan to commit genocide twice over ­ with no way out.