Why Did You Lie? contains three plot strands. In the first, four people – strangers to each other – are dropped off at a lighthouse atop the inhospitable rocky outcrop of Thrídrangar, three of them to perform maintenance, the fourth to take photographs of this harsh environment. It's supposed to take one night, but they soon discover their stay is likely to be prolonged. In the second, a policewoman, Nína, is struggling to cope in the aftermath...

A luxury yacht crashes into a Reykjavik pier. But the boat is empty; no one is on board. What has happened to the crew? And what has happened to the family who were very much present when the yacht left Lisbon? What should Thora Gudmundsdottir, the series sleuth, make of the rumors that the vessel was cursed? She is spooked even more when she boards the yacht and thinks she sees one of the missing children. Where is Karitas, the glamorous young wife...