This episode is the fourth and final part of the Excelis arc, starring Iris Wildthyme and Bernice Summerfield.
Benny has treated herself to a nice holiday in Brax' luxury spaceship (albeit without his permission), just to get away for a while from the Braxiatel collection, from life as an Adventure Archaeologist and from being a mom. She accidentally lands in Excelis after its nuclear destruction and immediately bumps into Iris Wildthyme, who's come to get her handbag back. Also, barbarians catapult pestilent animal corpses into the city to spread disease among those trapped inside.Excelis is still a wasteland and filled with dying lepers, so Benny and Iris throw on a leper disguise and get their drink on at a local tavern. They're overheard discussing the Relic and are unceremoniously captured. While escaping, Iris finally remembers the truth; the Relic is an organic bomb, and the people of Excelis are its fuse. As they die and fill its artificial afterlife with the energy of their "souls", the bomb would eventually destroy an oncoming space fleet led by an evil Queen. The guy in charge of all the dead animals, Snyper, sheds his human guise to reveal his true alien insectoid form, and reveals that he has taken other guises throughout the millennia; Iris knew one of them as Sister Jolene. She and the Mother Superior set this all in motion, the last survivors of their race planning revenge on the Queen who all but wiped out their species — and using Iris, the one person whom the Queen trusted, to prime the bomb which would destroy her. Benny depowers the handbag, rendering the entire plot moot.In the aftermath, the people of Artaris vow to rebuild their society, and Iris gleefully reveals to Benny that she's quite aware of who she is and what friend they've got in common.