Hidden in Saint Petersburg’s famed Mariinsky Theater are the world’s tiniest ballet fans: the Mariinsky mice, including Esmeralda, a rising dancer in the Russian Mouse Ballet Company. Despite being unable to control her tail, Esmeralda has just been assigned the lead role of Clara in a ballet debuting at Christmas: But when she learns that the new ballet features mice as villains, her excitement turns to horror: the mice of Saint Petersburg will never come to see such a production. Meanwhile, nine-year-old Irina is convinced that the mice she’s seen in the Mariinsky — the mice her father, the custodian, is supposed to exterminate — are not only fans of the ballet, but dancers themselves. No one will believe her, so it falls to Irina to help save the mice everyone else considers vermin . . . and perhaps to help Esmeralda ensure the future of the mouse company. Sweet and inventive, Kristin Kladstrup’s ballet fantasy features artwork by beloved illustrator Brett Helquist, old-fashioned drama, and just a touch of holiday magic.