Young mouse Calib Christopher dreams of becoming a Knight of the Round Table. For generations, his family has led the mice who live just out of sight of the humans, defending Camelot from enemies both big and small. But when Calib and his friend Cecily discover that a new threat is gathering - one that could catch even the Two-Leggers unaware - it is up to them to unmask the real enemy, unite their forces, and save the castle they all call home.

Sir Dinadan and his friends Sir Palomides, Sir Gaheris, Sir Terence, and other knights of the Round Table and their associates try to stop Mordred and his White Horsemen from ending King Arthur's rule of Great Britain.

Realizing that resistance to the inclusive culture they envisioned still remains, twelve-year-old nonbinary hopeful knight Callie and their friends continue to fight for the heart of their kingdom.