Ten years, later, eight years after the events of "BioShock", Subject Delta mysteriously comes back to life. Since both Andrew Ryan and Frank Fontaine are both dead, Sofia Lamb took over Rapture. Instead of being a society based on objectivism, a philosophy that believes people should only do things based their own self-interest, Rapture is now a collectivist society, or a society where people can only do things that help others. Sofia Lamb does experiments to figure out how to turn her now-teenage daughter, Eleanor, and everyone else in Rapture into the perfect humans. This is so that Rapture can become the perfect society, since Sofia believed a perfect society was not possible unless its people were also perfect. Subject Delta wants to rescue Eleanor before Sofia finishes her experiments.