After the first three successful Excelis tales, Big Finish closed the Excelis series with a coda set just after The Green-Eyed Monsters. The story sees Benny leave the Collection in Brax's living shuttle heading towards the dying world of Artaris, where she meets a “Trans-temporal Adventuress” by the name of Iris Wildthyme…
Stephen Cole's script seems designed to prevent those who have not been following Bernice's continuing adventures from becoming alienated by elements of the ongoing story, and it explains Benny’s slightly tetchy attitude throughout the story well. The way in which this story is tied into the rest of the trilogy is very intriguing indeed, showing that events have been in motion for much longer than anyone expected and there was more to Excelis than just the rise and fall of Warlord Grayvorn. Cole develops his own ideas well with those behind the animal undead being particularly sound, although given their unspeaking nature it does require some overt explanatory dialogue, but given a similar situation from the fifth Doctor tale The Land Of The Dead, it's kept firmly in the background.
Lisa Bowerman has been playing Benny for a long time now, and this shows through her assured performance, which is fantastic. As with her (then) sole performance to date in the Doctor Who main range, The Shadow Of The Scourge, Bowerman demonstrates that she is a perfect choice for Benny. Katy Manning's performance as Iris is also superb - some of the time, Iris comes across a little more sinister than she usually does (a wee bit seventh Doctor-esque), but perhaps this is the result of having Cole writing her instead of her creator Paul Magrs, but it's appropriate for this story that has a harder edge to it than Magrs' stories have tended to have in the past. Trevor Littledale is the most impressive though, immediately creating an impression as the prophet Snyper who seems to know much more about the events occurring than he's letting on. Kate Brown also excels as the Empress Vitutia, and although Stewart Alexander's Aaragon is somewhat unmemorable at first, he does grow in stature throughout the story.
The music and sound design by David Darlington works wonders here just like with the other Excelis stories beginning with a score that reflects the fact that Excelis has returned to a state of barbarism rather than advancement. While Excelis Decays ended the Doctor Who part of the series with a bang, The Plague Herds of Excelis ends it by tying up loose ends - especially Iris' - and adding something tangible enough for it to be considered as important overall to the series.