In Ennis, Alaska, the men that operate a research station vanish. To solve the case, Chief Danvers and Navarro will have to confront the darkness themselves, and dig into the haunted truths that lie buried under the eternal ice.

While Connolly threatens to transfer the Tsalal case to Anchorage, Navarro and Danvers make a discovery that brings the former colleagues closer together.

While searching for Clark, Prior asks Danvers about the case that strained her partnership with Navarro. Sifting through Clark's trailer, they find a lead about another Tsalal worker. Danvers clashes with her stepdaughter.

While investigating connections between Tsalal and Silver Sky mining, Navarro saves Leah from a violent protest. Kate McKitterick of Silver Sky cautions Danvers against pursuing the case.

When night falls in Ennis, Alaska, the eight men who operate the Tsalal Arctic Research Station vanish without a trace; to solve the case, detectives Danvers and Navarro will have to confront the darkness they carry in themselves.