In the early 15th Century PD, four centuries before the Havenite-Manticoran Wars, young immigrant Stephanie Harrington is adopted by a treecat that she later names Lionheart. The revelation that a native sentient species lives on the planet Sphinx draws interest from all over human-inhabited space. Stephanie and her friends and allies, some of whom also become treecat adoptees, have to fight a number of battles on various stages to make sure that Lionheart's species remains protected.