Season synopsis
Contains spoilers for this season and earlier seasons.
During the winter darkness in Ennis, Alaska, researchers disappear from the Tsalal station, leaving a severed tongue behind. Police chief Liz Danvers and trooper Evangeline Navarro connect it to Annie Kowtok, an Indigenous activist murdered years earlier. The researchers' frozen bodies are discovered outside town, but Raymond Clark is missing. Danvers and Navarro's uneasy partnership revives an older conflict while the town's mine and polluted water become part of the investigation.
Navarro loses her sister Julia, whose worsening distress ends in her death in the sea. Danvers struggles with stepdaughter Leah's involvement in Indigenous life and protests against the mine. Deputy Peter Prior discovers connections between the company and Tsalal, while his work damages his marriage. His father Hank, acting for the mine's interests, kills witness Otis Heiss. When Hank threatens Danvers, Peter shoots him, then stays behind to conceal the deaths.
In the hidden laboratory, Clark admits that the researchers concealed pollution that helped their work and killed Annie after she destroyed their research. A group of Indigenous women explains that they discovered the truth and forced the scientists into the cold in revenge. Danvers and Navarro decline to expose them, closing the deaths as a natural event. Clark's recorded testimony about the mine is leaked. Danvers survives falling through the ice with Navarro's help, but Navarro's later whereabouts remain unresolved when officials question Danvers.