In most worlds, the true origins of Adam was never discovered, Sigma was never bonded to a Little Sister, and those that survived the horrors of Rapture stopped fighting upon leaving the city for good. In this world, the paths of Brigid Tenenbaum and Eda Clawthorne cross just before a certain Ace in the Hole reaches Rapture. And the fate of many changes forever..... in particular that of Sigma's own daughter, Luz Noceda. https://tvtropes.org/pmwiki/pmwiki.php/Fanfic/BigSisterOfTheOwlHouse Now has a TV Tropes page