The BioShock games pose a simple question: “Why did you do that?” Like every other shooter ever made, they give you a goal to pursue and rules on how to reach it, but BioShock and now BioShock 2 go a step farther to ask why you’re so eager to follow every order you’re given.

Both times, the game fumbles the answer. In BioShock, you learn that your protagonist was brainwashed to obey any instruction that starts with the phrase, “Would you kindly...” The joke here is that you, the player sitting at home, have been following all these orders anyway, because that’s what the game told you to do. But the twist falls apart later in the game, when you start following Tenenbaum’s orders just as blithely as Atlus’. Why do we trust her? Wasn’t she a Nazi or something?

BioShock 2 doesn’t ace it either, but they start with a stronger hook: you take the role of a Big Daddy, who’s pair-bonded with a Little Sister named Eleanor. In the opening scene, you watch as she’s yanked away from you, leaving you in a coma – but you revive a decade later and come running after Eleanor, because - well, why? Why do you care about saving this girl? Because you’re her dad, of course.

(Major spoilers follow.)

But what makes you a dad? Late in the game, you raid the laboratory where Fontaine Futuristics turned you into a monster. At one end of the lab, in a dank pit like a mad dentist’s office, lies the apparatus where you and Eleanor were pair-bonded: a big table and a little chair, with a hose in between. Ever since that moment, she’s counted on you to fend off the crazies around Rapture, and you’ve needed her because, well, if she dies, you’re a goner too.

Is the bond between you “real”? What makes you a parent, anyway – your emotions, your actions, or chemicals? BioShock 2 bets on the chemistry, and it takes guts for them to say it. No parent, no matter how much they love their kids, could tell you why. I’m a dad, and I love my kid. I’ve loved him ever since I saw him bouncing around on the ultrasound, and no amount of tantrums, ER bills or diarrhea could change that. He’s a great kid and sure, I’d jump in front of a bus for him. But why?

It’s not a rational thing. Kids are just pets that can hit you up for money. As soon as they’re old enough to be useful, they move out. Our pair-bond is a trick of evolution as much as anything else. That’s also why people are so drawn to “bad parent” stories, about the dad who abandons his family or the mom who drowns her kids in the tub. It’s not the murders that fascinate us, but the fact that that bond could just vanish, like somebody flicked a switch.

The whole time you’re chasing after Eleanor – who’s your daughter, not by love, but through crime, corruption, and mad science – you’re supposed to ask why. But when it answers the question, BioShock 2 starts to stumble. As a gameplay device, Eleanor starts off with a single function: she’s your goal, the princess you have to save. When you finally find her, you watch a horrific cutscene where Dr. Sofia Lamb – the natural, but unfit, mom - appears to kill her before your eyes. This is pure stagecraft: Eleanor survives, but your physiological bond to her has been broken.

The game and the script disagree on what this means. Ludically, you’d think that saving Eleanor has become an optional goal, because now you can survive without her.  But as far as I can tell, there’s no way to finish the game without saving her. The bond was severed to set up a bigger point, which Eleanor puts eloquently: “Love is just a chemical. We give it meaning by choice.” Yet the gameplay never gives you that choice. You can’t leave without her, and you can’t “harvest” her, so by default, I guess you still like her.

But that’s fine, because the rescued Eleanor comes in handy. No longer a helpless kid, she now serves several functions. She’s a status gauge, to measure your moral decisions in the game; a mini-map, who tells you where to go next; and best of all, a combat resource, who’ll fight by your side anytime you summon her.

As gamers, we dig this Eleanor, because she’s kicking fantastic ass and helping us finish the game. We’ve left the child-stage of Eleanor’s life, the stage where she’s totally dependent on you, and moved to the part where she’s useful. But narratively, it’s all a whirl. Our little girl has turned into a shit-talking soldier in a steampunk-meets-Portal get-up. Coming in just the last couple hours of the game, it’s like watching her entire adolescence flash before your eyes. And by the time you get to the surface, Eleanor has become something else: your legacy.

Whatever bond you have with your kids, you can only shape them so much. Maybe you raise them right. Maybe you screw them up. Maybe you do your best, and they hate you anyway.  But at a certain point, it’s not up to you. The BioShock 2 team was smart to make Eleanor a reflection of your actions, but they were smarter to push you out of the picture.  As the game wraps up and you succumb to mortal wounds, you realize that Eleanor’s an adult. All you can do is let go.

Chris Dahlen writes about games, music, pop, and tech. You can find him online at @savetherobot, or drop him a line at chris [at] savetherobot.com.