A few days after Christmas, the step-sisters Ida and Tuva go on a winter dive in a secluded part of the Norwegian coast. Towards the end of the dive, a slip of stones catches Tuva under water. As Ida comes to the surface to seek help, she discovers that the landslide has also occurred on the surface, and the equipment, phones and car keys are buried and they are unable to receive help. As the desperate race for survival begins, Ida is subjected to the ultimate test of character and strength. During the Idea fight to save Tuva, the troubled relationship between the two sisters comes to the surface, and when all seems lost, the stakes rise beyond mere survival.