"To the Abandoned Sacred Beasts" is set in a fictional world resembling 19th-century America, where a civil war has ravaged the land. The conflict pits the North against the South, with the North employing genetically engineered soldiers known as "Incorruptibles" to secure victory. These soldiers are humans transformed into monstrous forms, imbued with extraordinary abilities to turn the tide of battle. However, their transformations come at a cost: the gradual loss of their humanity, leading to mental instability and uncontrollable violence.

The story begins after the war's conclusion, as the Incorruptibles, no longer needed, are hunted down and eliminated by the government to prevent them from becoming a threat to society. Nancy Schaal Bancroft, the daughter of a slain Incorruptible, seeks revenge against Captain Hank Henriette, a former leader of the Incorruptibles who is now tasked with hunting his former comrades. Nancy's father, known as the Beast of Gévaudan, was killed by Hank, and she vows to avenge his death. However, as she travels with Hank, she begins to uncover the complexities of his mission and the tragic circumstances surrounding the Incorruptibles.

Hank, also an Incorruptible, struggles with his own deteriorating humanity while carrying out his grim duty. His transformation into a werewolf-like creature symbolizes his internal conflict, as he grapples with the guilt of killing his comrades and the fear of losing himself entirely. The narrative explores themes of loyalty, morality, and the consequences of war, as Hank and Nancy encounter other surviving Incorruptibles, each with their own tragic stories and struggles. These encounters reveal the human cost of the war and the ethical dilemmas faced by those who created and used the Incorruptibles as weapons.

As the story progresses, Nancy's perspective shifts from vengeance to understanding, and she becomes determined to find a way to save Hank and the remaining Incorruptibles from their fates. The series delves into the bonds formed between Hank and Nancy, as well as the broader implications of using human lives as tools of war. The narrative is driven by its exploration of the blurred lines between heroism and monstrosity, as well as the enduring impact of trauma on individuals and society.