A deadly virus spread by rainfall forces siblings Simone and Rasmus to seek refuge in an underground bunker, parting ways with their scientist father.

After six years of isolation, Simone and Rasmus encounter other survivors. To stay alive, Simone must prove herself useful to the group.

Simone and the others set out for Apollon headquarters in Sweden, but their trek through Copenhagen is fraught with peril.

Jealousy flares in Martin and Beatrice. Simone and Rasmus meet a doctor with a connection to their father. A memory haunts Jean.

Lost in the woods, the group stumbles upon a mansion. The residents invite them to stay the night, and Lea bonds with one of the women.

A band of armed strangers tries to extract information from Patrick. Rasmus begins to unravel in the wake of a grim discovery.

The group arrives at Apollon headquarters, where Simone learns startling truths about the virus, her father and Rasmus.