Note: the page through the link is in French.
From the website:
The action takes place in Boston in 2025.
The city has been hit by a storm of dark fog that residents simply call later "the Fog" . This fog destroys everything in its path, plunging the world he left behind in the chaos. It is unclear the exact extent of the damage. Fog semblance settle permanently on the areas it touches, making them so dangerous, almost impassable and infested with mutants are all lethal threats.
The vast majority of the population seems to be infected with Fog and those who were not killed are infected to the point of turning into violent creatures, ruthless, equipped with superhuman abilities and are constantly chasing the survivors .