On Christmas Eve, three children receive presents that their late mother left for them before she died. Clara (Mackenzie Foy) receives a box she cannot unlock, but at her family's Christmas party, she follows a clue into a magical world, where she learns that she is the heiress to one of the enchanted realms and must help them stop an invasion. It's an expansion of the classic story The Nutcracker and the Mouse King by E.T.A. Hoffmann.