Into the Mist

It's the year 5003, and things are about to change drastically-for those who can endure it.
Nike Redd and her younger brother Freddie live in the Third Faction, or the 'Bottom', the absolute poorest faction in existence. They've never had much, but they did have friends.
Ash and Brendan Colby are slightly older than Nike and Freddie, but, as members of the First Faction, they were one of the only reasons that the Redds had been able to survive for so long.
But when the factions and everything above ground is destroyed by a mysterious, deadly green fog, none of the classes matter anymore, for the Factions cease to exist. Not many had survived, and with all of the crops and plant life, as well as buildings and animals completely dead and unlivable, there may be only a short amount of time before the rest of humanity goes along with everything else.