BioShock 2 takes place during 1968 in the fictional city of Rapture, an underwater metropolis hidden from the rest of the world. Rapture is founded by billionaire Andrew Ryan, who builds the city to escape the tyranny of governments or religion. Free from regulation, the citizens of Rapture begin "splicing", genetically modifying themselves using a substance derived from sea slugs called ADAM. ADAM is used to create "plasmids" that enable superpowers such as the ability to create lightning or pyrokinesis. Class conflict and civil war is exacerbated by the harmful side effects of ADAM overusage. Modified and conditioned children called "Little Sisters" collect ADAM from corpses and recycle it, and armored "Big Daddies" protect the Little Sisters. Rapture descends into civil war, and the city becomes a crumbling dystopia populated by Splicers, the spliced remains of the citizenry. After the death of Andrew Ryan, the dissident Sofia Lamb and her followers assume control of the city.