November, 1967, Iceland. Fourteen-year-old Marsi has a secret penpal – a boy who lives on the other side of the country – but she has been writing to him in her older sister's name. Now she is excited to meet him for the first time. But when the date arrives, Marsi is prevented from going, and during the night her sister Stína goes missing – her bloodstained anorak later found at the place where Marsibil and her penpal had agreed to meet. November, 1977. Stína's disappearance remains unsolved.

It's been several years since Detective Jimmy Perez left Shetland. He has settled into his new home in Orkney, the group of islands, off the northern coast of Scotland, with his partner Willow Reeve and their growing family. One stormy winter night, his oldest and closest friend, Archie Stout, goes missing. Ever the detective, Perez catches a boat to the island of Westray, where Archie worked as a farmer and lived with his wife and children. But when he arrives he finds a shocking scene.

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.

Was the biggest case of his career the worst mistake he ever made? Ten years ago, DCI Jack Logan stopped the serial child-killer dubbed "Mister Whisper", earning himself a commendation, a drinking problem, and a broken marriage in the process...When another child disappears a hundred miles north in the Highlands, Jack is sent to lead the investigation and bring the boy home. But as similarities between the two cases grow, could it be that Jack caught the wrong man all those years ago?

The body of a young Russian woman washes up on an Icelandic shore. After a cursory investigation, the death is declared a suicide and the case is quietly closed. Over a year later Detective Inspector Hulda Hermannsdóttir of the Reykjavík police is forced into early retirement at 64. She dreads the loneliness, and the memories of her dark past that threaten to come back to haunt her. But before she leaves she is given two weeks to solve a single cold case of her choice.

At a former sanatorium in the north of Iceland, now a hospital ward, an old nurse, Yrsa, is found murdered. Detective Hulda Hermannsdottir and her boss, Sverrir, are sent to investigate her death. There, they discover five suspects: the chief physician, two junior nurses, a young doctor, and the caretaker, who is arrested following false testimony from one of the nurses, but subsequently released. Less than a week after the murder, the chief physician, is also found dead, having apparently fallen from a balcony.

When perpetual bachelor Gunder Jomann goes to India for two weeks and comes home married, the town of Elvestad is stunned. On the day the Indian bride is supposed to arrive, the battered body of a woman is found in a meadow on the outskirts of town. None of the "good people of Elvestad" can believe that anyone among them would be capable of such a brutal murder. But in his quiet, formal way, Inspector Konrad Sejer understands that good people can commit atrocious deeds, and that no one is altogether innocent.

Eva Magnus and her daughter are out walking by the river when a man's body floats to the water's surface. Eva goes to call the police, but when she reaches the phone, she dials another number altogether.

Alex Armstrong has changed everything about herself—her name, her appearance, her backstory. She’s no longer the terrified teenager a rapt audience saw on television, emerging in handcuffs from the quiet suburban home the night her family was massacred. That girl, Alexandra Quinlan, nicknamed Empty Eyes, was accused of the killings, fought to clear her name, and later took the stand during her highly publicized defamation lawsuit that captured the attention of the nation. It’s been ten years since, and Alex hasn’t stopped searching for answers about the night her family was killed.

Detective Sergeant Chris Waters got the call at 05.29 that July morning. This is it, said DCI Reeve, you'll be first there, it's all yours, you're the crime scene manager. Suddenly, after months of waiting and wondering, Waters finds himself in at the deep end, and alone at the scene of a puzzling murder. As the investigation proceeds, the detectives at Kings Lake Central find themselves visiting familiar places and talking to some familiar faces, while old enmities reappear in the incident room. Before this is over, Chris Waters will need to make a career-changing decision.