National Bureau of Investigation joins the investigation and Nina is forced off the case. Tracks in the snow give her a new lead, however.

Raunola, the man suspected for the murders is leaving the investigators confused. The virus investigation takes a bad turn, and Nina and Thomas find each other in surprising place.

Both crime and virus investigations are progressing slowly. Work and personal life are starting to mix for both Nina and Thomas.

Virus investigation becomes even more topical. Police track down the fourth victim.