The Fortress

Esther is busy identifying the source of the disease when the bacteria appear in an unlikely place; Charlie runs the risk of being deported; Ariel is assigned her first big job: to write a speech preventing panic from spreading in Bergen.

Esther approaches a politician for help to reveal the source of the disease; Leo pleads with Esther to leave Bergen before she catches it; Charlie, believed to be infected with the disease, is to be sent away from the farm where he works.

Esther is pressured to develop a vaccine against the resiliently mutating bacterium; PM Heyerdahl employs stringent measures to prevent the disease from spreading; Charlie gets progressively sick; Ariel's brother wants her to join him.

Esther works on developing a vaccine but is shocked to learn the bacterium is turning more aggressive; on the verge of death, Charlie is saved at the last minute; PM Heyerdahl's drastic decision forces Ariel to reconsider her loyalty.

Some help from an unlikely source leads Esther to discover the bacterium's natural combatants; Heyerdahl and Zara bump heads over his plan to save Norway.