Little Sisters (originally named as Gatherers) are young girls who have been genetically altered and mentally conditioned to reclaim ADAM from the corpses around Rapture. Little Sisters are always accompanied by a Big Daddy. The Little Sisters are almost completely immune to damage but have no offensive abilities. Approaching or attacking them, however, will incur the wrath of their Big Daddy protectors. When the player defeats these protectors, the player can choose either to harvest or rescue the Little Sisters, with consequences for the storyline. Little Sisters are usually hiding in the air vents hidden around Rapture, they will only come out when being called by a Big Daddy.