When I hired a friend to look at Light Thickens as a story consultant, one point she made was that I could not kill off the koala.  “Your protagonist has invested so much energy in saving this critter,” she said,  “the reader will feel cheated if it doesn’t survive.  And there’s a maxim in the entertainment industry that you can’t kill off the family pet.” 

Old Yeller notwithstanding, Fido has to survive.  The problem here is that a koala is not Fido.  A koala is not a family pet. 

The plot of the trilogy is speculative fiction.  (I’ve been told there are two genres in speculative fiction: if it has magic and wizards, it’s fantasy.  If the magic is delivered by futuristic machines, that makes it science fiction.)  So the plot of Light Thickens  involves some magic.  But outside the magic of machines, the plot must rest on truth.  What is the truth?  https://www.savethekoala.com/deborahtabartsdesk.html