The movie is a retelling of E. T. A. Hoffmann's short story "The Nutcracker and the Mouse King" and Marius Petipa's The Nutcracker Ballet, about a young girl who finds a Nutcracker doll among the family's gifts and is charged by her parents to take special care of it.
The story revolves around young Clara who needs a magical, one-of-a-kind key to unlock a box that contains a priceless gift. A golden thread leads her to the coveted key, but it soon disappears into a strange and mysterious parallel world. In that world, she meets a soldier named Phillip, a group of mice and the regents who preside over three realms. Clara and Phillip must now enter a fourth realm to retrieve the key and restore harmony to the unstable land.