When a body of a woman is discovered at a lighthouse in the Icelandic town of Akranes, it soon becomes clear that she’s no stranger to the area. Chief Investigating Officer Elma, who has returned to Akranes following a failed relationship, and her collegues Sævar and Hörður commence an uneasy investigation which uncovers a shocking secret in the dead woman’s past that continues to reverberate in the present day.

Detective Inspector Matt Lockyer has been side-lined to working cold cases, following a bad decision he made in a recent investigation in order to support a friend. Lockyer isn't too bothered though, as it gives him the chance to review some of the cases that keep him up at night and to look into his own brother's senseless killing, which still remains unsolved. On a quiet afternoon, Lockyer receives a phone call from prisoner Hedy Lambert—a woman he put inside for murder 14 years ago. She informs him that the man she was originally accused of killing has turned up alive and well.

D.I. Duncan McAdam is dispatched home to the Misty Isle. A body has been found buried in a remote location on the Waternish peninsula. Well-preserved in the peat, Isla Matheson—missing for the better part of two decades—is revealed to a shocked island community. A teenage runaway is dead...and no one is talking.

Detective Inspector Karen Eiken Hornby has returned to the main island, Heimö, after many years in London and has worked hard to become one of the few female police officers in Doggerland. So, when she wakes up in a hotel room next to her boss, Jounas Smeed, she knows she's made a big mistake. But things are about to get worse: later that day, Jounas's ex-wife is found brutally murdered. And Karen is the only one who can give him an alibi.

Trying to process a life crisis Gothenburg policeman, Dennis Wilhelmson, decides to take a trip to his quiet childhood island, Smögen.