Princess Kassie, daughter of the gods Caïssa and Mars, lives a charmed life in the dazzling kingdom of Chess Mountain, where chess pieces are alive and flourish as loyal citizens.

But when Kassie's best friend Dimitri mysteriously disappears and her parents are blamed, Kassie's world shatters.

War is declared, and the princess escapes to Earth on a mission to strengthen her kingdom. Chaperoned by a trusted (and fashionable) knight, Maurice, Kassie desperately misses her family. She masquerades as a student in a chess-loving classroom with a quirky teacher. Mysterious threats and clues make it hard to tell friends from enemies, and Kassie lives under the constant risk of abduction.

To her amazement, she finds she has much in common with her mortal classmates, who encounter their own daily struggles. By sharing the magic of chess thinking, Kassie empowers her newfound friends to face the challenges in their own lives, including dealing with the class bully.

But when their tormentor presses hard and kingdom enemies draw near, Kassie must choose whether to cut her mission short, or risk everything to protect Chess Mountain.

When the ultimate showdown takes place, Kassie must make her decision-with no time to spare.