In "Shadow Wolf" by Kathryn Lasky, one of the darkest truths about the MacHeaths is revealed: they deliberately harm young pups to secure a position within the Watch of the Sacred Volcanoes. This disturbing practice highlights their ruthless ambition and the lengths they will go to for power. Their actions reflect a deep moral decay, showcasing a willingness to exploit the innocent for personal gain.

This secret not only illustrates the MacHeaths' lack of compassion but also serves as a commentary on the corrupting influence of ambition. By sacrificing the future of young pups, they betray the very essence of loyalty and honor that those in the Watch should embody. The narrative uncovers the complexities of their character, making it clear that their quest for status overshadows the wellbeing of their community.