In winter, the black ice cracks like a gunshot across the lake, growing thicker and darker every night. Nearby, a frozen waterfall transforms into a fantastic, baroque structure with dripping buttresses, flying spurs of ice and translucent, sparkling towers. The schoolchildren call it the ice palace.

When eleven-year-old Unn arrives in the village, she avoids the other children: she lives alone with her aunt and nurses a secret grief. But her boisterous classmate Siss refuses to be ignored and the two girls strike up an intense friendship. That is, until Unn decides to explore the Ice Palace on her own, squeezing deep into its beautiful but chilling inner chambers.

When Unn doesn't return home, Siss must struggle to cope with the loss of her friend, without succumbing to an ice palace of her own making.