Lumi and her twin sister Ivalo have always been inseparable, sharing every moment in their Lapland orphanage until the devastating day Ivalo is adopted, leaving Lumi heartbroken and alone. Refusing to accept their separation, Lumi ventures bravely into the wintry wilderness on a determined quest to reunite with her sister, braving snow-swept forests and icy trails. What she discovers beneath the pristine snow cover transforms her journey: a hidden, bustling Christmas factory operated by cheerful elves, pulsing with holiday magic and preparation.

There, Lumi encounters Pyry, a mischievous, rule-breaking elf with a heart of gold who becomes her unlikely ally. Together, they embark on an unforgettable Christmas Eve mission aboard Santa's sleigh, racing through the northern night sky amid twinkling stars and swirling snowflakes. As challenges test their resolve, Lumi learns profound lessons about family bonds, courage, and belief.

This heartwarming adventure proves that even the coldest, darkest night holds the power to deliver the warmest miracles, illuminating the magic within unbreakable sibling love and holiday wonder.