What happened to Lara Marteinsdóttir?

Iceland, 1956. Fifteen-year-old Lára spends the summer working for a couple on the small island of Videy, just off the coast of Reykjavík. In early August, the girl disappears without a trace.
The mystery becomes Iceland's greatest unsolved case. What happened to the young girl? Is she still alive? Did she leave the island, or did something happen to her there?

Thirty years later in August, 1986, as the city of Reykjavík celebrates its 200th anniversary, journalist Valur Robertsson begins his own investigation into Lara's case. But as he draws closer to discovering the secret, and with the eyes of Reykjavík upon him, it soon becomes clear that Lara's disappearance is a mystery that someone will stop at nothing to keep unsolved . . .