Where S.T.A.L.K.E.R.: Clear Sky acted as a prequel to the S.T.A.L.K.E.R. series, S.T.A.L.K.E.R.: Call of Pripyat actually takes place in Pripyat, Ukraine, and following the events of the original game. The Zone is believed to be expanding outside its original radius and the mutated creatures are growing stronger -- there's the fear that the Zone may eventually eclipse Russia, and that's where much of the horror comes from this time around, rather than the fact the world has all but ended and survival is much more than eating and sleeping.
34. S.T.A.L.K.E.R.: Call of Pripyat