Arctic Circle is set in the unforgiving polar region, amidst the icy landscapes of Finnish Lapland. After Nina Kautsalo, a Finnish police officer, finds a dying prostitute in an old cabin in the wilderness, the ensuing criminal investigation takes a surprise twist when a deadly virus is discovered in the prostitute's blood. However, when Thomas Lorenz, a German virologist, travels to Lapland to investigate the virus, he and Nina suddenly find themselves in the middle of an exceedingly unusual criminal investigation that ends up forcing them outside the law.

Just months after a tragic loss, detective Sofia Karppi investigates the murder of a woman with ties to a Helsinki construction company.