A prequel to S.T.A.L.K.E.R.: Shadow of Chernobyl, Clear Sky returns to the Zone, the perilous forbidden territory surrounding the Chernobyl Nuclear Power Plant, where mutants, deadly anomalies, and roving factions of scavengers known as Stalkers vie for survival and the priceless artifacts the region produces. The player takes on the role of Scar, a hardened mercenary who survives a catastrophic emission of lethal energy and is taken in by the scientific faction called Clear Sky. Aligned with this group, Scar is given a dangerous task: to track and stop a band of Stalkers pushing ever deeper toward the heart of the Zone, an incursion that threatens to destabilize the fragile balance of the entire region. As he ventures through hazardous swamps, ruined settlements, and contested battlegrounds, Scar becomes entangled in the ongoing faction wars that grip the Zone. His pursuit gradually centers on a single elusive figure, the Stalker Strelok, whose actions lie at the core of the unfolding crisis.