the man already dead; Elizabeth uses her powers to pull them into an alternate reality where the man is still alive, but this has unintended side effects that others around them suffer from nosebleeds and mental anquish, and Elizabeth becomes fearful of her abilities. They eventually board an airship to escape, but it is brought aground in Columbia by Songbird who kidnaps Elizabeth. Booker gives chase, but is pulled into the future of the 1980s by an elderly Elizabeth. She shows him that without his rescue, she will become like Comstock, inheriting the city and using it to lay waste to the surface world below. Before allowing Booker to return to his time, the future Elizabeth gives him a message to give to "his" Elizabeth to help her control Songbird and allow them to escape. Booker frees Elizabeth from an observation laboratory and the two make their way to confront Comstock. Along the way, they learn that Elizabeth has been kept under control of the Siphon, a machine built by the Luteces into the statue to nullify her tear powers; they also learn that Elizabeth is not Comstock's biological daughter, though oddly shares his genetics, and Comstock had attempted to kill his wife and the Lutece's to hide this conspiracy. They reach Comstock and Booker confronts him about Elizabeth's identity. Comstock says Booker already knows and the reason for why Elizabeth wears a thimble in place of a finger. Booker kills Comstock in anger, but Elizabeth calms him down and tells him they need to finish destroying the statue and the Siphon to fully realize her powers. They do so by controlling Songbird, but when Songbird turns on them, Elizabeth transports them to the underwater city of Rapture, where Songbird is destroyed by the outside water pressure. Elizabeth guides Booker to the bathysphere lighthouse, revealing she can now see all possibilities based on choice as evidenced by an infinite number of lighthouses they can see. Elizabeth explains the nature of choice to Booker, revealing that Booker and Comstock are the same person: in one reality, Booker ran away from a baptism ceremony after his atrocities at the Battle of Wounded Knee, while in another, he accepted it and became the religious Comstock. Elizabeth reveals she is also Booker's daughter, Anna DeWitt, who Booker had sold to the Lutece twins to pay off gambling debts. They in turn were working for