Is the quiet town of Ivalo about to become the site of Finland’s worst mass murder. There’s a sign in the heavens that says it is. Read on as we bed you in for season four of Arctic Circle, arriving on Channel 4 in the UK at midnight on 9 February 2026, with the five episodes free to stream on Walter Presents from Friday 6 Feb.

Nina Kautsalo (Iina Kuustonen) is now chief of police in Ivalo up there in the Finnish arctic, and things are getting complicated. She now has a one-year-old called Santeri with her retired hockey player partner, Toni, plus her daughter Venla (Venla Ronkainen), who has Down’s Syndrome, to look after. Sometimes, she has to take Santeri to work with her, which seems to fit in alright for her colleagues… most of the time.

Her former boss Jaakko Stenius (Kari Ketonen) arrives in town with news that the FBI has been in touch. The Bureau thinks a terrorist they’ve been tracking is headed to Ivalo because of an upcoming space science conference. Important delegates from NASA and all sorts of other organisations are coming to observe D/24 UN302, also known as the Eiscat comet, visible in the night sky for the first time in 5000 years.

The comet may be significant to the terrorist, who guns down an FBI agent and escapes, but it also carries some meaning for a group of staunch Christians right there in Ivalo. Nina’s police crew has been drafted in to help protect the conference, but soon there may be a lot more to deal with.

While Nina deals with an accident on the frozen lake and Stenius’s arrival, over at the local old age home it seems someone has deliberately broken the furnace. The parts won’t be available until the next day, so the residents are moved into the dining room for the night to benefit from the warmth of the log fire. It all seems a little suspicious when the head of the facility sends all the other staff home early…

Then there’s the man and his mother out on the farm, messing around with the carcass of a pig. Why’s he extracting its blood? What is the mad zealotry they share?

Meanwhile, Nina’s sister Marita (Pihla Viitala), who came out of a life of drugs and prostitution in season one, is now deeply religious. Is she on the fringes of the Christian sect that seems to be looking to the comet for something? Her poor partner Esko has lost his job testing snow tyres, but more than that, his father is over in the care home. And at his hotel, Stenius is hearing strange, mumbling voices in the night.

This is just a fraction of what goes on as the near earth object drifts across the November sky. As with previous seasons, the new series of Arctic Circle moves quickly and feeds you with lots of information, with breaks here and there to marvel at the vast frozen lakes, evergreen forests (although I thought we were above the tree line), and some examples of incredible Nordic modern architecture. There is snow everywhere, and people even cross country ski to the grocery store.

There are proper Nordic noir vibes for you, with touches of deadpan Finnish humour on topics such as breastfeeding, police harassment and medical examiner jokes. Family is a strong theme in Arctic Circle, and the show often deals with science, such as the deadly virus in series one and now astronomy. But there’s obsession, too. The religious cult storyline is reminiscent of the Heaven’s Gate adherents in New Mexico – 39 of whom took their own lives believing the Hale-Bopp comet held the secret to their salvation as it orbited in 1997.

Discover more Finnish crime fiction, on page and screen, right here.