He hasn't slept well since Rapture. There are too many things waiting every time he closes his eyes. He's learned how to deal with most of them over the years. All but one.
Because the worst nightmares aren't of walking through endless labyrinths of metal and glass, pistol in hand and listening to the splicers rave from out of the gloom. They're not of the proving grounds and how the Little Sisters screamed when he moved too slowly and clawed hands tore them apart. They aren't the ones of Fontaine standing over him glowing with power, or how it felt when he pressed that button in Optimized Eugenics and the surgical instruments turned his vocal cords into scrambled eggs. They're not even the ones where he answers the phone, then snaps Brigid's neck and walks through the house they've built as a refuge for the little ones, slaughtering them one by one because would you kindly?
They're the ones from the very beginning. Because what Atlas was telling him had made sense. If he was willing to kill things that had once been men and women by the dozens in order to survive, why not one more? Two hours in Rapture had already taught him that just because something walked on two legs didn't mean it had any humanity left in it.
Before Brigid showed up, he was going to do it. What he had to. What was necessary to get himself and other people out of this madhouse.
In his worst nightmares, she's late.