Yes, and she's getting serious about it

Carrie looks at you with a stern face for a few seconds, then turns her back and leave the room. You're afraid you crossed a line without knowing. Is she okay with helping you to **** her little sister bot somehow not if she has to be kept captive? It looks strangely arbitrary to you. Fortunately, she comes back almost immediately with a pen and a pad and sits in front of you.

"Okay, we have to proceed methodically. I'll take notes. So, we have to make sure that..." she starts writing on a sheet of paper while thinking out loud.

• A) Cass can't escape or be rescued.
• B) Nobody can trace her disparition to us.
• C) Nobody gets hurt, including her - Except if you're into it? (she pauses and looks up at you, but you're too perplexed by her sudden seriousness to give an answer and simply shrug)
• D) She gets access to comfort, hygiene and health to an extent we have to discuss.

She looks at her notes, lost in her thoughts, while you stay puzzled by this sudden change. She's not simply playful anymore, you can tell she's dead serious and considering her options. It's both impressive and frightening. She suddenly start moving again and rip another sheet from the pad to write on it.

"The **** part will have to be thought thoroughly, but first there's a whole list of things we need to take care about the location where we will bring her. Even the smallest detail could ruin our plans. So :

• We need a building with a basement wide enough to contain all the necessary facilities. We have to buy it, we can't just pay a rent then have to move her later and risk leaving a shitton of clues behind us.
• The building should be remote so our coming and goings and the manual labors we have to do on the building won't draw attention to us. It should also be close enough so we could pay dayly visits to Cass. Even if you get bored of **** her, we won't be able to free her without risking to be arrested but I would still have to feed her and take care of her other needs.
• The place should look as bland as possible from the outside so nobody would think about intruding. Still, we need to put securities in case somebody wants to... I don't know... squat for the night. And the access to the basement should be even more secured. The basement should also be completely soundproof.
• We should probably install electricity and running water underground, unless you want Cass to live in the dark, stink like a skunk and pee on the floor. - she looks at you and add "I mean, it's still an option if you want to..." before resuming to her list.
• Her cell should contain only one room so she couldn't play hide and seek and use it to escape or ambush us. We should also install cameras to monitor her and cut the basement in two, with one part outside of the self from which we could see her wherever she is.
• We need to make sure she doesn't have access to anything she could turn into a weapon, so no flatware, nothing she could break too easily... Hmmm... Maybe not even sheets, I don't want her to hang herself.
• On a related note, we have to balance hygiene and safety. Could she drown herself in a bathtube, or use a shower pipe to hang herself, or break knob to make a weapon out of it? It's things we have to take into consideration.
• We also need to think about the walls, floor, door and all the furnitures with the same questions in mind, with hygiene replaced with comfort. Should we try not to make the place where she will spend the rest of her life too depressing, considering every effort we will make to make it more welcoming comes with its own expense and may need replacement in the long run?
• If we really want to take no risk, we can restrict her movement even more, by using bondage tools for instance. But we also have to take into consideration that restricting her movement too much could prevent her from keeping in shape and ruin both her health and attractiveness.
• What do we do if she gets sick at some point or need special treatments we can't provide her? Calling a doctor won't be an option.

You can't avert your gaze from your girlfriend planning the fate of her little sister in such details and detachment. You didn't think she could be so immoral, not just depraved but possibly devoid of guild or empathy, or at least so easily enclined to push them aside just to please you. You wouldn't have expected her to be so clever either, thinking so quick about all the bases you need to cover. Are you actually dating a sexy nymphoamniac sociopathic criminal mastermind? The prospect is terrifying, yet oddly arousing, yet intimidating, yet flattering considering she's doing all of it just for you. Your boner as never been as confused as it is right now and you have to resist both the urges to take her once again right here right now or flee and never turn back.

You suddenly realise she has stopped writing and is looking back at you, tapping her pen on her lower lip. "What do you think?" she asks.