After the death of their son in a car accident, Ana and Pablo decide to move to the mountains to open a country house. Their best friends, Guille and Bea, have come from the city for the opening dinner, but something goes wrong. A strange aurora borealis leaves them isolated, while Guille suffers a sort of attack, severely injures another, and tells an alternate version of their lives: he knows only Ana, his partner according to him, who died in the accident, but not their son, who is still aliv...