Return to Ivalo in Season 4 of Arctic Circle

In the midst of the Polar Night, the skies are illuminated by a rare comet.

Nina Kautsalo (Iina Kuustonen) has received worrying news: 24 residents of a local retirement home have been found dead of carbon monoxide poisoning.

Meanwhile, an international astrophysics conference is about to take place in honor of the comet. But the FBI has warned of a possible threat, prompting the Finnish Bureau of Investigation (KRP) to send Nina’s old boss Jaakko Stenius (Kari Ketonen) to investigate the issue.

Nina discovers clues that show maybe the mass death was not an accident, and she soon joins forces with Stenius. During the investigations, new evidence suggests that the emergence of the bright comet lighting the sky and mass death are related. In the end, the traces lead to a small religious group, whose members are willing to do anything to fulfill an ancient prophecy…