"Sue Cat" centers around a young girl named Sue, who discovers a mysterious cat with the ability to speak and wield magical powers. The cat, named Nyarla, reveals that it is a guardian spirit tasked with protecting the balance between the human world and the spirit realm. Sue is drawn into this hidden world when she accidentally stumbles upon an ancient artifact that awakens dormant supernatural forces. Together, Sue and Nyarla embark on a journey to recover scattered fragments of the artifact, which have been stolen by malevolent spirits seeking to disrupt the balance between worlds.

The narrative unfolds across multiple episodic arcs, each focusing on the retrieval of a specific artifact fragment. Along the way, Sue encounters a diverse cast of characters, including other humans who possess unique abilities tied to the spirit realm, as well as rival guardians and spirits with conflicting agendas. The series explores themes of trust, responsibility, and the consequences of wielding power, as Sue grapples with her growing role in maintaining the balance between worlds.

Nyarla serves as both a mentor and a source of comic relief, balancing the series' more serious moments with lighthearted interactions. Sue’s character evolves from a curious and somewhat naive girl into a determined and capable protector, driven by her sense of duty and her bond with Nyarla. The antagonists, primarily rogue spirits and corrupted guardians, challenge Sue and Nyarla with increasingly complex moral dilemmas, forcing them to confront the blurred lines between good and evil.

The plot is structured around a mix of episodic adventures and an overarching narrative, with each episode contributing to the gradual unraveling of the artifact's origins and its significance to both the human and spirit realms. The series maintains a steady pace, blending action, mystery, and emotional depth, while gradually building toward a climactic confrontation that tests Sue’s resolve and her understanding of the responsibilities she has undertaken.