The story of S.T.A.L.K.E.R.: Clear Sky brings the players one year prior to the events of the original S.T.A.L.K.E.R. game in 2011. A group of stalkers has for the first time reached the very heart of the Zone - Chernobyl Nuclear Power Plant, and brings about a cataclysm on the brink of a catastrophe. An immense blowout of anomalous energy changes the Zone. Stalkers and even expeditions die or end up sealed on the lost territories. New areas, which remained unknown since the time of the Zone emergence, appear on the Zone map. The unstable Zone continues to shake with blowouts. The anomalous activity is at its maximum, and the Factions War has started, catching the player at the edge of the opposition between stalker factions, Strelok and even the Zone itself.