ected ▁in ▁the ▁w are house ▁have ▁broken ▁down ▁the ▁door . ▁Grad ually , ▁the ▁rest ▁of ▁the ▁a partment ' s ▁residents ▁are ▁bit ten ▁and ▁inf ected . ▁ ▁Áng ela , ▁Pablo ▁and ▁Man u , ▁the ▁three ▁surv iv ors , ▁find ▁a ▁key ▁that ▁will ▁allow ▁them ▁to ▁escape ▁from ▁the ▁building ▁via ▁a ▁large ▁d rain ▁in ▁the ▁bas ement ▁that ▁is ▁connected ▁to ▁the ▁se wers . ▁Man u ▁is ▁bit ten ▁outside ▁the ▁a partment ▁of ▁the ▁key ' s ▁location , ▁forcing ▁Áng ela ▁and ▁Pablo ▁to ▁take ▁refuge ▁in ▁the ▁pent house . ▁They ▁discover ▁a ▁t ape ▁rec order ▁which ▁explains ▁that ▁the ▁pent house ▁owner , ▁an ▁agent ▁of ▁the ▁V at ican , ▁was ▁charged ▁with ▁the ▁task ▁of ▁isol ating ▁an ▁en zym e ▁carried ▁by ▁a ▁young ▁Portuguese ▁girl ▁named ▁Tr ist ana ▁M ede iros , ▁whose ▁sympt oms ▁suggest ▁a ▁demon ic ▁possession . ▁As ▁the ▁agent ▁attempted ▁to ▁treat ▁M ede iros , ▁the ▁en zym e ▁mut ated ▁and ▁became ▁cont ag ious . ▁The ▁agent ▁then ▁se aled ▁Tr ist ana ▁in ▁the ▁house ▁to ▁die ▁of ▁star v ation . ▁An ▁inf ected ▁boy ▁within ▁the ▁att ic ▁dam ages ▁the ▁light ▁on ▁Pablo ' s ▁camera , ▁requiring ▁Pablo ▁to ▁activ ate ▁the ▁camera ' s ▁night ▁vision . ▁A ▁now - g hou lish ▁Tr ist ana ▁emer ges ▁and ▁searches ▁the ▁pent house ▁for ▁food . ▁Áng ela