He's not sure when it happened—not that it matters so much as when it happened, but that it did happen.
The thoughts always seem to stampede through him, when a bullet passes by his eyes, when she screams, "Fireman!" or "Patriot!" or "Handyman!" because at these moments, he knows there is a very likely chance that he'll die, flooded to the brim with salts and wrapped with enough gauze to cover the skyline of New York.
He gets delusional, at times, and he'll blame it on the nosebleeds and the nauseating fuzz that develops on the roof of his mind, like a scattered rainstorm that refuses to leave him. It's at these times when he trips, shoulder buckling into a crate, or a wall of cover torn from another reality, another universe that she steals from. When shots pellet through his soft, human flesh, somehow missing all the vulnerable, recklessly unprotected areas that would kill him stone dead—he'll glance at her, as she scrambles from cover to cover, shouting with frantic eyes, "I'll find you something soon!" while at the same time, she manages to throw him extra clips of ammo or a pack of coagulants from a discarded first-aid kit.
He'd never imagine a tiny little helpless girl maintaining his survival in a floating city with death flying from every angle. Mere days ago, if someone tried to feed him some cock-eyed story like that, he'd think they'd be smoking something out of a vermin spray can.
But now, splattering the last henchman's brains against the once beautifully paved walkway, he falls to the ground with a round in his thigh, a hole in his side, the devil whispering in his ear—before the whisper turns to something sweet. Elizabeth's voice. It cuts through the muck and stays his spirit or his soul or whatever it is that makes him—while she sticks him with something, and wraps him with something, trying to fix him into a brand new man when all she manages is a heavier disfigurement. And it's alright, because when he stands, she smiles at him like he's her only hope in the entire world. It's even more depressing when he acknowledges that he is. And when did that begin to mean anything?
"How did a girl your age learn to patch up a dyin' man?" he asks her once.
"I read about it in books. What else would I do up in that tower?" she answers flippantly.
It's a bad hand she was dealt, as he watches their journey harden her from something pliable and fragile into something adaptive, desperate, and still, though unwarranted, fragile. Nineteen, he thinks, her eyes listless when she gleans over the innards and guts of men splattered for God and the devil to see.
When he was nineteen he…
He'd done much more damage than what she's seeing. He wouldn't wish his experiences on his worst enemy—though, he decides he'll make an exception for Comstock, when they find a secluded area in the shadows of a back alley, when she cries one silent tear, then two, slowly paving their way to her neck, when she believes him to be sleeping.
But he shouldn't care—he hasn't cared about anything since—and why should she mean that much?
A few days ago, she was bursting at the seams when she'd hear music, running off to dance like a deprived child, eying cotton candy and hot dogs like they were exotic treats meant for only the most seasoned traveler, asking which choker charm she should choose because they were both just so pretty—
Then he killed a man, and she'd gotten progressively quieter. Then Lady Comstock became a stranger who'd never given birth to her, and she grew bitter. Then she realized how much of her life was a sham, and he'd never witnessed such a beautiful creature mature so darkly or so acceptingly in so short amount of time.
And yet, she wrapped his hand after the first massacre she'd been present to watch, his bloodied hand embracing that scarf like a lover. She knocked him out when he set the coordinates for New York. She saved him with a blimp she made magically appear when she hadn't wanted him anywhere near her—she came off as a bundle of contradictions, until he cared enough to realize that trust through skepticism was all they had. She'd have to keep him alive for him to keep her alive. She was smart, smart enough to the point he wished she wasn't.
Then he told her to call him Booker, and she told him about her thimbled deformity.
"Stay with me, Booker," she says, voice strained with heated stress. She pushes something into his bleeding chest. It might be her hands, it might be a needle. "You're going to be fine. It's just a scratch; I'll fix you in no time, okay? Okay, Booker? Stay with me."
When did she evolve from being a means to an end to being only a means?
He's in a daze when she tries to revive him, mind running like a broken faucet.
It wasn't when she asked him why people treated each other with such cruel intent. It wasn't when she wrapped his hands around her neck, demanding his word to kill her when the time came. It wasn't when he tried to console her through the door in the airship after she stabbed Fitzroy in the heart. It wasn't when she told him about her pinky-I've heard they're all the rage in Paris. It wasn't when she told him her only perpetual acquaintance was a bird made of metal.
Maybe it was when he had to chase her across the beach. When he had to cut short her wondrous, wondering eyes across the small vastness of the only world she'd ever truly seen.
"Booker," she sighs in relief. He breathes in a stable, deep round of air.
He looks up into her crystal blue eyes, and he thinks, maybe, she began to matter when she tried to make him dance with her, on the deck of that fabricated sea. When she twirled and twirled and laughed, while others watched her with lost awe, clapping in time with her beat.
No. It was a long time before that. And why can't he know something so simple? So on the verge of his periphery, something that's there but isn't?
It's probably because of what he's doing to her. Her childlike glee and untainted innocence, of dancing laughter and freedom-it was something he took away. Is still taking away. He's leeching it from her like a parasite, running her through roads of blood. And even if he brushes that off, tells himself he's done things far worse in his past, it is still a death he'll add to the count.
He opens his mouth then, to offer something stupid like an apology or an explanation he's not sure what about, but she stops him by wrapping around him in a grateful hug.
"That was a close one, Booker. Really close."
It is brief, and he doesn't want to call it a hug because that isn't what it was. Then she's standing up, reaching an arm down in an offer to help him up.
There have been moments that have made him wonder, but it's in this one where he finally sees the depth of her strength. Resilience bubbles up inside her reservoir of hope, and her specific brand of innocence he believed to ebb away remains quietly, hovering in her eyes with an unbroken spirit.
It is clearer when he has to start keeping up with her as she threads him along, chasing after her resolve to face her father. To face her life. To face what makes her what she is, who she is and who she will become.
Through all of that, she still looks over her shoulder, making sure he's there.
So he stops asking, stops wondering, stops trying to make himself stop. Because he's always known that it didn't matter when; only that it does.
And so he follows her.