So, I had a vague inspiration for a plot that would go somewhat along these lines. I'm very suggestible and willing to change the plot up to meet my partner's desires, as well, so if you have any ideas or if this inspires something in you, let me know and I'd be more than willing to discuss it with you! Here's the general idea I had.
The worst possible place you can get put is Claremoor prison. It's full of the biggest, baddest, and worst of all, cruelest prisoners in X-place (maybe Miami? I was thinking somewhere warm, but I'm fine with wherever, really). This is where the big guns get put when they get caught, and it's overfull with murderers and drug dealers and quite a few drug kingpins, as well as mobsters. My character would be a young man who had come from a slew of foster homes, eventually deciding that rather than stay in them, he'd live on the streets. He would have gotten into some petty drug dealing and drug use and been busted for it, (or maybe cybercrime, with identity theft and such...haven't really decided yet. If you have a preference, let me know.) and after badmouthing the wrong judge on the wrong day, gotten thrown into Claremoor to soften him up a bit.
Here's where your character would come in. Mine would get thrown into a cell with your character, one of the most infamous prisoners. He'd preferably be a drug kingpin or a mobster, and while he himself isn't particularly violent, he's known for ruling his section of the prison with an iron fist, and even the guards would be under his thumb. Your character would be looking for a young man to satiate his desires, and with the prison overfull, that very young man, my character, ends up tossed into a cell with yours.
I'd like for the roleplay to evolve from there, with mine getting out after a relatively short stretch, and then yours winning his defense appeal and getting out shortly thereafter. I'm thinking that my character would then move in with yours, or at the very least continue their relationship. This could be anywhere from some light non-con or bondage all the way up to stuff better left in the extreme section. I'm quite negotiable on this.
Anyways, that's the rough idea. Please PM me or post here with any interest!