A double murder sends Maria to Stockholm where she runs into a familiar face.

Just as the Medieval Week is about to begin in Visby, the seventy year old woman Frida is assumed dead in an arson. When several murders occur, the traces lead Maria Wern and her colleagues to a quaint village where everyone knows everyone. The discovery of some documents in Latin and incomprehensible drawings turn the police's suspicions towards the rituals of the Medieval celebrations.

When Maria Wern of the Gotland Police Department receives anonymous death threats, she and her colleagues begin a frantic search to track down the source. Following a violent assassination attempt, however, she is ordered off the island for her own protection. Together with a group of old girlfriends from school, she secretly heads off to the pristine nature reserve of Stora Karlsö Island.

In the midst of the midsummer celebrations on the island of Gotland, a series of vicious murders take place with occult overtones. A man is found strung up alongside slaughtered animals; another is found sacrificed in his car in the middle of a summer meadow. The holiday paradise is shattered and soon attention falls on an old murder case involving a long-deceased killer that someone is clearly mimicking...

Two women, seemingly unconnected to each other, die in apparent suicides. But the strange circumstances cause Maria Wern and her colleagues at the Gotland Police Department to dig deeper, and soon the questions multiply. Was someone stalking the women? Is there reason to believe that they were suffering from some kind of psychosis? And is there a common denominator after all?

It’s Christmas on Gotland when the island is suddenly struck by an unspeakable tragedy — a high-school girl is found dead in the middle of a country road wearing a white Lucia gown. What at first appears to be an incomprehensible suicide soon proves to be something far more sinister, when behind the innocent facade it turns out that a group of girls at the local high school is harbouring dark secrets...

A ten-year-old boy disappears from a dinner in a little fishing village, while another vanishes from a refugee camp on the island. These are but the first in series of frightening events to take place on the island of Gotland, where a string of brutal murders are committed in quick succession. And what starts out as the search for a missing child, leads Maria Wern and her colleagues ever deeper into a nest of hidden agendas, personal betrayals — and links to international crime.

After intervening in a fist fight and getting beaten up herself, Maria heads the investigation of a woman who was murdered close to the place where Maria was assaulted. The murderer most likely witnessed what happened to Maria. The motifs oscillate between revenge for infidelity and hatred towards homosexuals, and as the number of murders increase so does Maria's frustration over the reluctance from neighbors and potential witnesses to collaborate in the investigation.

The charred body of a medium is found in the gutted remains of her office after a fire. And it soon turns out that she was murdered —suffocated with a plastic bag and doused in kerosene, the woman was left to die in the flames. When another two murders take place in the same manner, it becomes clear to the Gotland police that they have a serial killer on their hands - but without having the slightest idea what the victims had in common, or who the next one might be.

A double murder sends Maria to Stockholm where she runs into a familiar face.