A box of photo albums is found in the attic of a house in Höfn, a small fishing village on the south coast of Iceland. The new owners return it to the man who sold them the house, along with a muddied child's shoe with a name written on the sole: Salvor. The man is baffled; they never knew anyone called that. Shortly after the phone rings - it's the nursing home where his mother, an Alzheimer's patient, lives. She's suffered a heart attack and the doctors don't expect her to live much longer. The nurse asks him to let his sister, Salvör, know as well. Their mother has been asking for her. Jóhanna is a member of a search and rescue team in Höfn and she's searching for two couples from Reykjavik. Their phones' last location has been pinpointed as the road leading up into the highlands. It's far from clear why these people would have made such a risky trip in the middle of the harsh winter, and they soon find the first dead body. More troubling, Johanna senses her team is being tracked out in the snow. Hjörvar works at the Stokksnes Radar Station in the highlands. He is alone when the phone connected to the gate rings. It's the first time it's done so since he began working there five months ago. He picks up the phone but can hear only interference and what sounds like a child's voice asking for her mother.