So, from an ask I got on my tumblr about Bruce watching Joker dance, I ended up writing this.

He doesn't mean to stare. He never does. But, as always in situations like these, what Bruce means to do and what he actually does never match up. He should be cuffing Joker right now, dragging him into the car and driving him back to Arkham, making the city safe for however long the staff can keep him contained. But he isn't. Instead Bruce is watching Joker through a gap in the dust covering one of the windows, as the soft music playing inside reaches his ears.

Bruce has been here for over ten minutes, which is nine minutes too long and there's a lie Bruce usually tells himself around about now, when the line between surveillance and voyeurism starts to blur, that this is necessary, that chances to watch Joker unawares are few and far between, and, when dealing with a man as dangerous as this, he needs all the study he can get. And it is a lie and Bruce knows it, but the part screaming at him to smash through the window and end this isn't strong enough to fight the part that keeps him rooted to the spot.

It's the way Joker moves, hypnotic and irresistible, hips swaying in time with the music, a body that's too much and too little in all the wrong ways so much more graceful than it has any right to be, gangly limbs twisting and bending with the sort of practiced precision that makes it look effortless. He's a good dancer and Bruce wouldn't be surprised to learn Joker was one in his previous life. He's a good singer, too, the gentle baritone that's spilling promises of love and romance reeling Bruce in.

He vaguely recognises the song, most people would, but Bruce's head is too focused on Joker to give it a name. All he sees is that body in purple pants and an untucked shirt and he wants to slide his hand underneath to feel the way bone and muscle shift under the skin, see if it feels as soft and fluid as it looks from up here. His pulse is racing, face getting warm as his mind then moves to a different sort of dance, one that happens between sheets, that has that body moving under his and he should look away, but he wants - needs - to see more and his hand comes up to press against the glass before he can even stop it.

His skin itches and his breathing is getting heavy and he knows the line has been crossed now, which is almost enough to finally make him leave, but Joker's turning and his eyes find Bruce, catching him in the act. A smile spreads across Joker's mouth and in a way that tells Bruce his presence hasn't gone anywhere near as unnoticed as he thought, Joker says, "Don't be shy," and beckons him inside.

Bruce should leave now. He should but he doesn't. He's opening the window and gliding to the floor and Joker's coming nearer, body still flowing with the music in that hypnotic way. And their hands meet as an arm slips around Bruce's neck, breath hot on his cheek as Joker's voice drops to a whisper. And Bruce's body responds in ways he knows it shouldn't as his palm lands on that tiny waist, pulling them even closer together, before dipping under the fabric and finding out that, yes, Joker is every bit as soft and fluid as he hoped. But he's also sharp, tight with tension in the way his hand grips Bruce's just a little too hard and nails scratch against the back of the cowl.

Bruce's fingers dig into Joker's skin, pinching and kneading, making Joker's voice catch and he doesn't have a chance to continue the song where he left off because their mouths come together, as any chance Bruce pretends he might've had to leave is gone. He's committed to the dance now, the one that has him tearing open buttons and pulling down zippers as Joker opens latches and locks, the singing now taking the form of gasps, giggles and moans.

And then that body is finally where Bruce wants it, bending and swaying and twisting up against him, hands going places Bruce never admits he wants them to be until they are, and he can't do anything but follow Joker's lead, let himself be guided into a rhythm that isn't polished or flawless but instinctive and raw and all the better for it. It doesn't last long, time is a luxury neither of them have, but that doesn't stop Bruce imagining what it could be like, taking his time, fingers and lips exploring Joker's body inch by inch. But the fantasy breaks down as they both start to unravel and it's nothing but heat and sweat and legs around his waist, heels in his back, fingers in his hair, body trembling as sounds he'll hear long after he's left hit his ears.

Bruce follows right after Joker and when he's finished has to stay very still for a very long time. His head rings, chest hurts and he can't quite remember how he got here or why. But he knows he has to leave. He gets dressed without a word and, just like last time, swears this won't happen again, but when Joker comes near, naked and free of shame in a way that almost makes Bruce hate him, Bruce knows it will.

And when Joker kisses him, he kisses right back, the taste of blood as teeth take his bottom lip a reminder of why he shouldn't do this, but always will.