In the beginning was the Word.

Then God created music. Harps and timbrels, cymbals and cornets, he made them all.

Words and music became songs. And God saw that it was good.

He was not alone in that view. From the first instant he heard voices raised in melodious praise, a blessed sound that rejoiced in life and light, Castiel tapped his toes as he went about his Father's duties. If he sometimes timed his arrival or departure at gatherings where music was being played so that his wings beat in time with the music, well, it was merely coincidence, no matter what Uriel might mutter. Uriel had no sense of rhythm, whereas it was a gift with which Castiel had been liberally endowed.

­*****

Dean Winchester has not yet become accustomed to Castiel's unannounced arrivals. He no longer reaches for his gun when he realises he is not alone, but he still jumps, a reaction which he often attempts to cover with a demand for pie or beer. Castiel has learned that these demands are not to be taken literally and that Dean is merely exchanging pleasantries. After all, it is part of Sam Winchester's function to go out for food and drink.

Castiel has, however, made some concessions to Dean's preferences. These days Castiel does not make his presence known to Dean until he is sure that Dean is not engaged in any activity which might cause a negative reaction to his arrival. He has learned it is counter-productive to interrupt Dean when he is watching one of the special television shows that has little in the way of script but much celebrating of the flesh. His vessel still bears the mark on its forehead from the glass ashtray that Dean had flung at him before he had understood this. Similarly, there is no point in attempting to talk to Dean when he is in the shower. At least the shampoo bottle that hit him when he tried to do so did no real damage to his vessel.

Tonight Dean is waiting for Sam to return with their evening meal if his mutterings of "Come on Sammy, a man could die here" and frequent glances at his watch are anything to go by, and he is not watching anything particular on the television set, simply flipping between channels in a way that Castiel finds – oh. Oh dear.

That has not happened for aeons: Castiel losing control of his vessel so that he becomes visible to mortals without willing it to be so.

Dean jumps as he becomes aware of Castiel, but Castiel is transfixed by the television screen which is showing dancing the like of which he has never seen, performed to a joyful chorus of women's voices which are celebrating staying alive.

Dean is speaking but Castiel does not know what he is saying. The screen is taken up with a man dancing on a floor lit by beautifully coloured lights. He is mesmerising, moving as one with the music, his body a sinuous interpretation of the song as he seems to glide over the floor, an illusion only helped by the way his pants are oddly wide at the bottom of the leg.

"Dude!" Castiel comes back to himself when he finds Dean's fingers snapping in front of his face. "What the hell?"

With an effort he focuses and delivers the message with which he was entrusted, but as his gaze returns to the screen Dean's reaction becomes a barely-heard background litany of "fucking" and "cryptic" and "angels", arranged in increasingly inventive ways.

He eventually removes himself from sight, but can't quite tear himself away from the room while Dean leaves the television on, even when he goes back to flipping through channels in a way that Castiel finds both disorienting and highly disappointing. Every now and then there'll be a glimpse of the lights and the dancing, with that wonderful music, but Dean always moves on swiftly to another channel.

When Sam comes back with food and Dean turns his attention away from the television, Castiel finally leaves. He has work to do.

*****

Castiel realises after a while that it is perhaps fortunate his vessel practised yoga so fervently. His body might otherwise have suffered some lasting damage as he faithfully follows every last instruction on the DVDs he has purchased.

He is thankful that time spent watching over the Winchesters has alerted him to the existence of such things as Post Office Boxes, which means he can procure these things without Uriel's knowledge. It's not that he's avoiding Uriel's scorn. It is simply that he wishes to master the intricacies without interruption.

*****

"Stop the car."

Dean jams on the brakes at the urgency in Sam's voice. Luckily there's nothing behind them.

Sam's staring back at the sidewalk they've just driven past. So far as Dean can see from the rear view mirror it looks just like every other stretch of sidewalk they've driven past in the last ten minutes: dark, empty apart from a small group of people lurking around a badly-lit doorway, and distinctly devoid of anywhere serving food.

"That was Cas," Sam says.

"And just what would an angel be doing walking around in this part of town? No, tell me Sam, what would an angel be doing walking at all?"

"Dean." It's been a good half hour since Sam's bitchface last made its appearance, which has got to be some sort of record. "I'm telling you, it was Cas. If we follow him maybe we can help stop another seal being broken."

Dean just hates it when Sam's right. Glancing over his shoulder, he does a quick u-turn and pulls the car in at the other side of the street, just in time to catch a glimpse of a very familiar-looking trench coat disappearing through the group of people as its wearer makes his way towards the doorway.

He doesn't really want to leave his baby in this sort of area, but an opportunity like this is just too good to miss.

"Let's go," he says, checking his gun.

"Uh, Dean, I don't think you're going to get that in there," Sam says.

Biting back the obvious retort – he has such self-control – Dean instead satisfies himself with a "Huh?"

"It's a nightclub," Sam says. "Bouncers. No guns allowed."

"Castiel's gone clubbing? This I have got to see." The prospect almost makes up for having to leave his gun in the car and walk in there practically unarmed.

As he gets out of the car, Dean sees what Sam had noticed due to him not having to drive and watch the road for traffic and shit. There's a neon sign above the doorway through which Castiel had disappeared, advertising a nightclub, or rather a N gh lub!.

As they near the doorway, the group that had been standing there turn and go inside. They look like your average bunch of losers, but Dean knows not to assume too much. It's not like Lilith has high standards when it comes to picking her foot-soldiers.

Sam suddenly stops dead in his tracks. Following his gaze, Dean sees a tatty poster tacked up the wall beside the door. A tatty poster which changes everything with a few ten-inch high words: Thursday night is disco night!

"No," Dean says. "I don't care if this is the sixty-sixth seal and Lilith herself is in there, I am not going in, Sam."

Sam just shrugs. "Okay. I'll go in on my own," he says. "Let's hope I don't need backup."

"In case the boogieman gets you, you mean?"

Sam's exasperated sigh wipes the grin off Dean's face - how was that not awesome? - and despite knowing that he's being well and truly played with no pretence at subtlety, Dean follows in his brother's humourless wake. He's glad of the reassuring feel of the silver knife strapped against his calf. He can't let Sam go in there alone not knowing what he might encounter, not if whatever it is has been enough to bring Castiel here.

So they pay their cover charge – "You don't think it's a bad sign we don't have to wait in line, Sammy?" – and are admitted to the hallowed precincts. Or at any rate, they're allowed to go down dark cement stairs that seem to suck at Dean's boots, putting all of his instincts on high alert. He takes point when they get to the bottom of the stairs and are faced with black double doors; pushing through the left-hand one he notes they're scarred and worn, before he concentrates on what lies on the other side of them.

They appear to be in a dimly-lit room, which has a bar along the opposite wall and chairs and tables arranged haphazardly on the – goddamn sticky - carpet. There are about thirty people in there, most of whom are turning to look at Dean and Sam as they make their way across the room. Dean can't tell if they're being watched because they're just too damn cool for this place, or if it's because it's about to be chow time. With Winchester on the menu.

With their backs safely to the bar, Sam and Dean continue scoping out the place. To the left there's nothing of note except for the blonde in the little black dress that is really quite little. To the right, there's what has to be a dance floor. That's when they see it.

"Is that - ?"

"Oh yeah."

They're screwed. They are so screwed.

Brooding in malevolent silence, casting its unrepentantly evil spell over the scuffed floorboards of the dance floor, is an honest-to-God disco glitter ball.

"Dean, Sam!"

And that is an honest-to-God angel coming towards them. An angel who has squeezed his way into the tightest white flares that Dean has ever seen and far tighter than he ever wants to see again, thank you very much. Not to mention a shiny blue shirt that he's got unbuttoned practically to his navel, meaning a large expanse of smooth muscled flesh is on display. And then there's the huge flared collar, which kind of reminds him of the shirt Sammy wore when they did the demon on a plane gig. The nightmare picture is completed by a chunky medallion hanging from a gold chain around Castiel's neck.

Dean's hand is biting convulsively into Sam's arm. That might or might not account for the breathless and squeaky nature of Sam's greeting.

"Cas. What a surprise."

"I didn't know you came here too," Castiel says, looking bizarrely delighted.

Dean clears his throat and lets go his death grip on his brother's arm. Time to get control of the situation.

"So you're undercover," he says. "In 1970?"

"I am here to sing to the Lord a new song," Castiel explains. "The psalteries and the lyres have been replaced, and this new discotheque music is heavenly indeed."

Later, when this is over and the memory decently salted, burned, and buried, Dean will deny that anything leaves him speechless. For now, he simply opens his mouth and then closes it again.

Sam wades into the breach. "Uh, your clothes," he says, intelligent and articulate as ever.

"They are correct in every detail," Castiel confides delightedly. "They are even made of polyester. I found something called a specialist supplier. Like the places you go to for your herbs and your books."

Sam's eyes seem glued to Castiel's tight white pants. "Not quite like that," he says. "Not unless there's something Bobby isn't telling us."

Dean hits him. "Dude. That's just nasty."

They've lost Castiel's attention anyway because the air is suddenly filled with ominous noise.

"It's starting," Castiel says, his voice raised so they can hear him over the caterwauling. And if Dean didn't know better, he'd have sworn Castiel looks excited as he moves towards where lights are now strobing the dance floor.

"Shifter?" Dean suggests.

Sam raises his eyes from where he's started to inspect Castiel through the camera on his cell. "I wish," he says.

They end up retreating to the bar. God knows Dean needs a drink. He's still not entirely sure what Castiel's doing here but it's looking less and less like a case and more and more like this is the end of the world as he knows it.

"Apocalypse now, please," he mutters into his beer, but the universe fails to oblige. This is particularly unfortunate because standing at the bar gives them a grandstand view of the dance floor.

"Dude, I thought angels were supposed to be graceful."

"Dean, tell me he's not…"

"He's not," Dean says immediately. Because the alternative doesn't bear thinking about.

But he is. Dean closes his eyes for an instant as Castiel, apparently caught up in the moment, does the splits. When he opens his eyes again, finding they're watering in sympathy, that damned angel is doing something quite extraordinary to the blameless floor, judging by the movements of his hips.

"Dean, don't you think we should -"

"Nu-uh, Sammy. If he wants to scare off the Apocalypse, who are we to stop him?"

"He's gonna hurt himself – or somebody else. And he's your angel."

"You know that guy?" It's the blonde in the black dress, who tears her eyes away from Castiel long enough to make sure Dean knows she's talking to him.

"No!"

"Yes."

Unfortunately they say it at the same time, and then Sam stomps on Dean's foot and says more loudly "Yes."

She turns her eyes back to the figure in the middle of the empty dance floor, who's jerking around like a marionette whose strings have first been electrified and then dipped in water and then possibly electrified again before half of them have been cut.

"Figures," she mutters. "The cute ones are always either gay or weird."

And really, watching Castiel, his big gold medallion bouncing as he steps and claps in time with a rhythm only he can hear – which is almost precisely half a beat behind the one on the song that's playing – Dean finds he can't mount any sort of protest which wouldn't label himself as weird.

He would have come up eventually with something that would prove him the exception to the rule, except that Castiel is strutting round the dance floor as the song's chorus approaches and – and – oh, God. There is prancing and kicking and hip-thrusting, not to mention other things involving hands gesturing at crotches – or one crotch, singular, and not so angelic right now - that Dean just doesn't have words for.

There is also singing. They can't hear him over the music but the lip synching is, unfortunately, unmistakable as Castiel shimmies his hips and sashays around the dance floor.

"He is D–Desirable, he is I–Irresistible, he is S–Super-sexy, he is C-Castiel. O, O, O – He is D.I.S.C.O."

The worst, well, almost the worst, of it is that people who had started off by laughing at the lunatic in the tight shiny outfit with the humungous gold medallion nestling against his exposed chest, which is beginning to gleam with sweat, now seem to be getting into the spirit of the thing. Some of them are even jigging around on the spot as Castiel wiggles his hips, his face raised adoringly to the glitter ball. He positively glows as the shafts of reflected light play over him, highlighting his expression of rapture.

Dean's getting seriously worried that he's watching a resurgence of the most evil thing to plague mankind since Paris Hilton. Well, actually, disco had happened before Paris Hilton (just), but the principle is the same. If the way disco fever is sweeping through this room is any indication, the whole world is at risk.

"This is all kinds of wrong, Sam. We gotta stop him."

"He's not hurting anyone."

"He's scarring people for life."

"Seriously, Dean. He looks –"

"Like he's getting his inner Jennifer Beals on," Dean agrees quickly. Lobotomised 70s rejects look freaking stupid. They do not look happy.

There's a minute's silence – apart from the noise masquerading as music – during which Sam's bitchface contorts meaningfully from pissy and demanding to pleading and you're my brother and I know you don't really want to pick on the angel with no sense of freaking rhythm because he's such an easy target.

Dean sighs.

"His funeral," he says, turning and shouldering his way towards the door through the small crowd that has now gathered around the dance floor. And then he suddenly cheers up.

"Wonder if Uriel knows," he says, and reaches into his pocket for his cell to take a photo. When he turns round, he almost drops the cell. Sam isn't with him.

"Sam?"

He's not panicking. Not yet.

Full-blown horror doesn't start until his gaze finally finds his brother, out there on the freaking dance floor where Castiel is still enthusiastically prancing. Sam's jerking around like a crazed lunatic, his long arms flailing manically as he throws his head back and sings at the top of his voice. "Dancing queen, feel the beat from the tambourine."

"Fuck. Fuck, fuck, fuckity fuck, Sammy," Dean says before years of training finally reassert themselves - but he can't be blamed for that because who the hell would ever think this an eventuality for which he needed to be trained? – and the appropriate response kicks in. "Christo."

It doesn't seem to have any effect, so Dean takes blackmail photos instead.

After a couple of minutes even that stops being fun, and Sam's still – well, he's not quite sure what Sam's doing, but it's not pretty. Dean can feel a headache coming on.

Castiel appears finally to notice he has company out there, and he's making his way over to Sam, just as fast as the pointing and hip-cocking routine he's got going will allow. And that's when Dean gets his totally awesome idea and heads over to the DJ, who looks as though he was dead and buried before the 70s happened the first time round.

Dean is awesome. He is way too awesome for Sammy to appreciate the full awesomeness that is his big brother, but he thinks Sam's about to have an inkling when the music stops abruptly, leaving Sam mid-convulsion, before some high-pitched disco freak starts crooning "More than a woman".

It's gold, that's what this is, as Castiel moves tight into Sam, pulling him close before attempting to dip him.

Scuttling backwards in panic, Sam's feet get tangled around one another and he goes down hard. Dean can almost hear the thunk as wood meets wood. Sam's left lying there like a beached sasquatch, rubbing the back of his head and staring up at a very puzzled-looking Castiel.

Dean can't actually hear the exchange of words that follows, but it involves Sam scrambling to his feet, waving his arms around again, and then retreating. Fast. By the time he reaches Dean, his gaze is fixed resolutely on his feet. Which is probably as well, given the way they just betrayed him.

It's one of those rare moments when Dean really doesn't need to say anything to have his kid brother flushed bright red and looking like he's peed his pants in public again. Not that he's done that for twenty years or so, Dean has to admit, but it never gets old.

"You gonna blame it on the boogie?"

Sam glares at him, before taking off through the doors. Dean takes one more look round, finding that Castiel doesn't seem too disappointed by the loss of his partner now that a few other people have made it onto the dance floor. Dean doesn't think he's noticed the way the blonde in the black dress is moving purposefully in his direction.

He's grinning as he follows Sam up the stairs and to the car. Sam's stomping all the way, Dean notes, like he's got rhythm in his soul.

Sam finally breaks his pissy silence when they're in the car.

"We are never talking about this."

"Whatever you say, Sammy."

He puts the car into drive.

"It's a tragedy we're leaving this funky town. We should stay at the YMCA. Or go to the car wash."

He never thought he'd see the day Sammy turned Metallica up so loud the whole car shook.

He turns the volume down slightly. He needs to be sure Sam can hear his phone ring when Bobby gets the photos.