Arctic Circle

A Finnish police officer discovers a dying Russian sex worker being held captive in a farm cellar, carrying a deadly virus. Meanwhile in Helsinki, the case comes to the attention of the European Center of Disease Control and its German virologist.

Authorities locate Raunola's snowmobile but he remains missing. Meanwhile, Nina is ordered to meet with Thomas and assist with the investigation into the Yemeni virus. As a result, all pregnant women in the area are ordered to get tested.

Nina tries to elicit a confession from Raunola for three murders, while Tomas continues testing pregnant women. However, when they try to test the women at an infamous ‘prostitution bus,' they find themselves face-to-face with an uncooperative guard.

Nina and Thomas comb through the list of Marita's sexual partners and focus in on a peculiarity in the year 2012, which they are intent to ask her about. Meanwhile, in Russia, Raunola is captured by the mysterious Maxim.

Thomas must give birth to a baby in an emergency, while Nina finds the prostitute who escaped her captor. The Laestadian church is reluctant to have members of its congregation tested, despite Dr. Lorens' insistence.