A/N Thank you to Voldy's Pink Teddy for the suggestion of the fire spell and thank you to the guest who suggested the use of the alkali metals. To be honest, that was the idea that got me going.

Enjoy:

Zombie Blues Part 2

They returned to Harry's hotel room, which, as it happened, was only the floor above Dean and Sam's.

"So," Sam started, his eyes narrowed and Dean playing with his gun on the bed, listening carefully. "The inferi can only be ganked by burning?"

"Complete combustion, yes," Harry said, nodding. "The issue is that if it's not burnt fast enough, and the fire goes out, it can recover."

"And considering these sons of bitches live in water, that fire'll go out pretty damn quick," Dean finished. Harry nodded again.

"So we need some kind of fire which won't go out from the fire. Haven't you got some sort of magic for that?" Sam asked, looking to Harry. The wizard grimaced.

"Not that can be conjured. There used to be a spell for Hephaestus' fire but it got lost with so many others when the Library of Alexandria burnt down. That was supposed to have been able to burn, even in the presence of water. Everything else gets put out sooner than we would need it." They thought for a moment.

"What about covering the surface of the water with oil or naphtha and setting light to it, burning those bastards as they get out?" Dean suggested. Harry shook his head.

"Inferi are intelligent enough to wait for it to burn out first, maybe even go around the back way."

"What if we set up a feed for them to get covered with flaming oil as they move down the passageway?" asked Sam. Harry considered it and then shook his head.

"It's a good idea, but they'll keep moving until it burns their hearts as that's where the magic is anchored. In that time, we'll probably be killed. Plus, they might have enough sense to jump back in the water.

"So, to get this straight, their hearts need to be burned first, and then the rest of them?" Harry nodded. There was silence as they considered it.

"Shotgun shells!" Dean said suddenly. The other two turned to look at him quizzically. "Shoot the suckers in their hearts with something that'll burn and then set fire to their remains." Sam bounced off that idea.

"Alkali metals!" he exclaimed. Harry frowned.

"What are the alkali metals?"

"You know, sodium, potassium and so on? Really reactive, explosively reactive, to water?" Dean told him. Harry shook his head.

"Tell me more. I didn't exactly have a typical education after eleven." Sam got into lecture mode.

"The alkali metals, group two in the periodic table, are highly reactive, as Dean said, to water. They have to be stored in oil or they'll start oxidising as soon as they meet the air which has water molecules in it. They are so reactive they aren't found as elements in nature: they have to be separated by electrolysis. Before electrolysis was invented, sodium used to be known as soda and potassium as potash." At the last sentence, Harry, whose eyes had started to glaze, perked up.

"Now I've heard of soda and potash! They're used in several potions, including a few poisons."

"Potions," Dean repeated incredulously. "What next? Do you fly on broomsticks too?" he asked sarcastically.

"Actually, yes," Harry replied absentmindedly, not taking any notice of Dean's face-palm: he was too busy searching inside a bag that looked decidedly bigger on the inside than the out. Well, if the fact half the wizard's body could fit in it was anything to go by, that was. "Here we are," he told the two hunters, flicking through the pages and pointing triumphantly at one. Crowding round, Dean and Sam noticed it was a recipe, though with rather odd ingredients.

"Eye of a newt?" Sam muttered as if he didn't believe what his eyes were seeing. "Tongue of a salamander, pickled in stewed moon petals?" Harry waved a hand dismissively.

"You should try having to pickle flobberworms' guts for two hours. That was my potion's teacher's favourite detention for those he didn't like. Which was most of the school. Here, see, soda." Sam raised an eyebrow. "What?" asked Harry defensively. "The wizarding world is typically two centuries in the past compared to the muggles. With magic, there wasn't the need for the developments that the muggles came up with." Dean cut the debate off as soon as he saw the interested look Sam had.

"So what's this potion for?" Harry scanned the text.

"Clearing blocked drains." Dean was disappointed.

"It's not particularly explosive, then?" Harry shook his head.

"But what if the soda was replaced with caesium?" asked Sam, a light entering his eyes. "Since Frankium's radioactive, caesium's the most explosive possibility out of the group." Harry shook his head.

"I don't know. I was pretty hopeless at school with potions and haven't got much better since. But I do know someone who is." Reaching into the bag again, he pulled out a mirror.

"What, you need to primp before going to visit?" asked Dean sarcastically.

"No, remember, it's magic. Hermione." Just about to ask why Harry was saying a girl's name, the Winchesters leapt back as a face appeared in the mirror, a woman's face.

"Harry?" The voice was female as well.

"Hi, Hermione. I've got a quick question, if you don't mind."

"Sure. I'm on lunch now, anyway. Are you on a hunt?" Harry nodded.

"You know the common drain-clearing potion?" Seeing her nod, he continued. "Would I be able to replace the soda with caesium without the whole potion being de-stabilised?" She frowned at him.

"Yes, you could, but you'd destroy your plumbing." He smiled at her.

"We were thinking more about destroying inferi." Her expression demanded elaboration. "I've got a nest of inferi to clear out. There's another pair of hunters accidentally on the same case and we've teamed up. They suggested shooting the inferi in the heart with an alkali metal." Hermione narrowed her eyes.

"Why not just use a fire whip?

"Too wet. Remember where I got the locket? Where Dumbledore got poisoned?" Her face showed dawning comprehension.

"That sounds a good idea, then. But the explosion won't actually set fire to the inferi, you know." Harry twisted his mouth in thought.

"We'll figure it out. Thanks for your help."

"Anytime. But remember, that potion will be really sensitive to water. Even touching the air for too long will make it go off." Harry nodded and the mirror went blank.

"So, we have our potion," Harry said, turning to look at the hunters. He blinked in surprise when he saw two gun muzzles pointing at him. Carefully putting the mirror down, he raised his hand up in surrender. "OK, what's going on? I thought we'd got past this stage."

"You have a spirit trapped inside a mirror," Dean accused him darkly. "That's so not right!" Harry frowned.

"I haven't got a spirit trapped anywhere. The mirror's a communication device. Think of your mobiles, only with picture as well as sound and no monthly pay-plan." Sam lowered his gun though Dean wasn't so trusting.

"That was a real person? Another wand-witch?" Harry nodded.

"Hermione's been one of my best friends since I was eleven. She's married to my other best friend and works in our government."

"OK, good, 'cause having a hot spirit chick trapped in a mirror would be sick and wrong." Dean finally lowered his gun, then a lecherous expression crossed his face. "Though think of the benefits... Ouch!" The last was because of Sam's sharp elbow. Dean glared at his younger brother, then turned back to Harry. "So, you say we have our potion, and, for the record, could you guys have been any more cliché?" Harry rolled his eyes.

"Yeah, to sum up, this potion will dismember the inferi, but won't actually set fire to them so, potentially, they could regenerate. It would take a lot of time, though."

"So we'll fill our shotgun shells with the potion, but have to work out another way to set fire to them." Harry nodded and silence fell for a few moments. Harry got an idea and looked up, a smirk curling on his lips.

"Here's the plan….."

The next morning three adult humans trudged down to the beach, one wizard, armed with his wand, and two muggles, armed with highly explosive potion-filled shotgun shells. Harry took out a small, sharp knife and splattered a little blood on the doorway, quickly healing himself as the rock shifted aside. They stepped inside and, by the doorway, Harry started drawing an odd symbol on the ground.

"Remind me what that's for?" Dean asked idly.

"It'll attract the inferi more than just the prospect of fresh meat will: we want to get all of them, after all." Dean nodded.

"Gonna let a little light on the subject?" Harry sent up a couple of witch-light balls: they wouldn't go out until he put them out, but he'd be able to use other spells as well. The only reason they weren't used as much as lumos was because lumos was mobile and more like a spotlight compared to the balls' ambient light. But for this purpose, it was perfect. He activated the rune and they all tensed as they heard a wet slap from down the passage. Dean and Sam slunk off to the side, taking a little shelter in the small alcoves that were everywhere along the wall.

"Got your portkeys?" Harry checked. They nodded at him, tense. They didn't have to wait long before the first inferius came into sight. The sharp report of Dean's shotgun was heard and the inferius staggered back. The three watched anxiously until the inferius exploded, the shell having leaked enough potion to do the job. Harry summoned the remains closer to him and set fire to them: they didn't want to scare the other inferi off with a wall of fiery body bits. They shared a quick grin of triumph before starting the process again with the next inferius.

It seemed timeless, Harry thought in the midst of the explosions, the shots, the fiery infernos. The inferi just kept coming, more and more each time. Dean and Sam had fallen back a little, needing more space to shoot into the ranks. They were barely managing to reload in time to prevent a messy death, sometimes. Harry was reassured they could get away if necessary, but he wasn't sure they would think of their portkeys if it got too late.

When there were no more inferi to take down, it came as a bit of a shock. The three staggered outside, welcoming the fresh air, and the dry warmth of the sun. Out in daylight they looked pretty frightful. Harry was covered in gore, having misdirected his summoning spell a couple of times and got showered with bits of corpse. The other two weren't much better. They had some unmentionable stains which would ensure the clothes' disposal as soon as possible. Both Dean and Sam had scratches: Sam even had a bite-mark on one hand that Harry took a quick look at and had to disinfect from where an inferius had got too close.

"Please tell me we got them all!" Dean begged Harry. The wizard wearily cast an auror-level spell that gave a vague impression of how much dark magic was around. There were traces: inferi were not exactly grey, but not nearly enough to indicate even one active inferius.

"Seems like it. I'll check back here in a couple of days just to make sure none of them have started regenerating, but otherwise, good job!" He smiled at them thankfully. "I'm really glad we teamed up. I'm not sure what I would have done without someone backing me up. There were just too many to deal with alone." Sam and Dean shrugged.

"It's what we do," Dean dismissed.

"Tell you what," suggested Sam. "You give us the information about how to kill a demon and we'll call it even." Harry nodded.

"I can do that. But….let's get cleaned up first!"

Settled comfortably in the Winchesters' room, the brothers prepared to grill Harry.

"So you're the 'demon expert' are you?" started Dean bluntly. Harry breathed in heavily.

"People call me that."

"Are they right?"

"In the course of my job, as in the course of your job, it's inevitable that I'll come across demons and their creatures. Almost more so in the Wizarding world, seeing as demon summoning rituals are so very common. Anything from a basic blood exchange for a favour to the full blown selling of a soul." Dean frowned.

"Wait, people actually sell their souls to those things?" Harry nodded. Sam interrupted before he could speak.

"Dad did, remember." Harry raised an eyebrow.

"Your father summoned a demon?" Dean looked away. Sam glanced at him, then returned his focus to the wizard.

"We're pretty sure he did. The clues…well, Dean was dying and then miraculously got better. Not long after that, Dad dropped dead. No explanation. Then, demons since have mentioned seeing him in Hell, though we're not sure they were telling the truth." Harry nodded.

"Yes, well that is one result of selling one's immortal soul to demons. Another, more troublesome pact is where the demon has fulfilled its side of the bargain and therefore owns the human's soul outright, but decides to use him or her as an Earthly slave rather than claiming the soul immediately."

"They can do that?" Dean was horrified.

"Unfortunately. And, as the human is not in any way possessed by the demon, there is no reaction to Holy water, nor can the influence be broken by an exorcism."

"So how can we stop the buggers if we come across them?"

"The human will carry a sign on their body. Usually over the heart, but it can also be on the back of the neck or around the wrists and neck. That's for identification. Once you know they're demon-owned, you kill them. At that point, the soul no longer has a body to live in and so will return to the demon." Sam frowned.

"It's not possible to save them?" Harry shook his head sadly.

"They made a bargain, they have to pay the price. The only way to save them is to convince the demon to give them up. And to be honest, most of the time, I don't bother trying."

"How can you be so callous?" Sam demanded. Harry shrugged.

"There's one thing you can say about demons and demonic bargains. The demon always makes sure the human knows exactly what they're bargaining with. They might not actually understand what selling their immortal soul means, but they know that that's what they're going to lose. And to be honest, there's enough literature out there which is reasonably accurate about the consequences of demonic bargains that I have no sympathy for them if they went in half-cocked."

"And what if they did it to save someone? Should they be punished for that?" croaked Sam. Harry sighed.

"Look, I don't mean to sound completely uncaring, but miracles come at a price. It might be the price of faith, of life, of health, of love, of eternity, but it always has a price. If you're not willing to pay the price, you shouldn't ask for the miracle."

"What do you know about it?" Dean demanded furiously, his face twisted. "You sit there with your damn stuck up attitude, condemning all those people, but what the hell do you know about it?" Harry smiled, but it wasn't one of humour.

"When I defeated Voldemort, I thought I would have to die. I walked to my death willingly. I died. There, I was given a choice to live or to move on. I chose to live. When I survived and killed Voldemort, I thought it was a miracle. I was alive, my friends were alive, my girlfriend was alive. People were dead, but far fewer than could have been killed. I thought there had been some sort of guardian angel looking over us.

"It was a miracle, but it wasn't free. I thought to achieve the miracle I would have to die. What I didn't realise was that I wasn't giving up my life, I was giving up my future. Five years on, married and hoping to start a family, I discovered I was sterile. My wife divorced me and I have to live with the knowledge that family, something I have always craved, was the price of peace."

"Do you regret it." Harry smiled again, this time more genuinely.

"Honestly? Yes. Sometimes. Then I think of that bastard and all he did to me, to my friends, to my world, and I know that I would do exactly the same thing again." There was silence. "Anyway, you didn't come here to hear my life story. You want to know how to kill a demon, then?"

"Yeah, properly dead. Not just exorcised." Harry nodded.

"Well, there are various ways. None particularly easy. There was that gun made a while back-"

"The Colt. Yeah, we know. That's not on the list anymore." Harry raised his eyebrows, but didn't ask.

"Then there are three swords which were made from the nails which pinned Christ to the cross. Nothing demonic can even touch those without feeling its demonic aura being shredded. A stab with one of those will kill a demon completely, even its main body in Hell." Dean and Sam exchanged glances.

"So where can we find one of those bad boys?" Harry ran a hand through his hair.

"Uh, well I think Michael Carpenter is still wielding one of them. He's in America somewhere. Another is borne by Sanya the Russian. I'm not quite sure where he is. The other is lost, or at least is not somewhere easily found at the moment." Dean nodded.

"OK, we'll have to look up Carpenter, then. Any other ways?"

"They won't give up their swords without a fight and believe me, with God's luck on their side, they're not the easiest opponents. If you know the demon's human name and can find its human remains, there's a rumour you can kill them that way." Sam frowned.

"What do you mean, a demon's human remains?" Harry's eyebrows shot up.

"You don't know that much?"

"Don't know what?" demanded Dean.

"Most demons were once human. They ended up in Hell after their deaths, often from selling their souls, and Hell corrupted them into powerful, evil spirits: demons. But like any spirits, they have to have some anchor to the world: their bones. I've never heard of a demon who was seen after its bones were burnt. Of course, if your demon was once an angel, that doesn't help much. What is the name of your demon?"

"We don't know," Sam said, sounding a bit shell-shocked. Harry supposed it would be a shock to hear that those they encountered had once been human. For a while Harry had been worried that he would one day have to fight Voldemort as a demon. Thankfully, Death had assured him that, apart from those wizards who sold their souls, magical beings went to another afterlife, separate from that of Heaven or Hell.

"OK, what do his demon eyes look like?"

"Yellow," answered Sam with horror in his voice. "This rancid, mustard yellow, shot through with white and black." Harry nodded, biting his lip.

"Probably a fallen angel, corrupted by Hell into being a demon." Sam frowned.

"You can tell that?"

"Yeah. White, red and black eyes were once human. Anything else means a former angel."

"What do those other colours mean? We've only come across black eyed demons. And Yellow-eyes. There are more?" Harry nodded.

"Black is just the common demon. Not particularly powerful, relatively, mostly pawns out to create chaos. Red eyed demons are the ones with enough authority and power to make deals. White eyes are the rank above: usually over a millennium old and powerful. Above them are the fallen angels who are even more powerful , but usually don't leave Hell. There aren't many of them left, thank Merlin! I've only heard of four so far: Azazel, who currently rules Hell, Samhain, Beelzebub, Abaddon, and Crowley. And Lucifer, of course, but short of an apocalypse, there's no need to worry about him. There used to be another couple called Hastur and Ligur, but as far as I know, they were destroyed a couple of decades back. I'm pretty sure there were more who fell with Lucifer, but either they're gone or just don't visit the human realm."

"Two were destroyed? How?" Sam asked urgently, focusing in on the bit that was useful to them. Though, the other bits were interesting and worth further research. Dean's expression gained a slightly more eager cast.

"I have it on good authority that Ligur was killed by angel-blessed Holy water and Hastur was smote by an angel itself*."

"An angel." Dean said flatly, his face falling from its hopeful cast.

"Yes. Being a demon's natural opposite, each anathema to the other, their auras give them an advantage against demons that humans don't have. Most effective anti-demon weapons have something angelic at the core of them. Personally, I reckon the bullets to the Colt had something of an angel in because it's the only explanation for why they could kill demons, and could never be reproduced. Obviously, having an angel kill the demon is best, but Holy water blessed by an angel is a thousand times more potent than something you could do, or even something blessed by a priest. An angel's Holy water will shrivel up the demon's inner being like a slug covered in salt." Sam nodded eagerly.

"That does sound as though it would work!" Dean turned to stare at him.

"Sam? Why're you going along with this? He's batshit insane! Angels don't exist!"

"They don't? Oh dearie me, I must have been mistaken that the being who came to tea a week ago was an angel! Do forgive me," he mocked. Dean glared at him.

"OK Sammy. We're leaving this nut-job to his crack-dreams."

"You could do that," Harry agreed "or you could come with me to visit him."

The bell tinkled. Dean glared at it. The merry sound just reminded him that he'd lost the argument. Worse still, he was in a bookshop. Seeing the unholy glint in Sam's eyes and the twitch of his finger, Dean mentally groaned. It was going to be as hard as Hell to pull the bibliophile out of this place. Seriously, Dean couldn't see the appeal. Loads of dusty books with dry, barely legible texts and pages that smelt like something long-dead. Harry led them to the front of the shop.

"Aziraphale?" he called.

"Just a minute," someone called back, his voice muffled by the door to the back room. It sounded rather posh and very British. The door opened and out came someone who looked uncannily like a librarian. Dean looked incredulously at the glasses, middle-aged spread and crows-feet. This was meant to be an angel? Then he saw the eyes. Deep pools of ancient blue, knowing and observant. Angel or not, the being called Aziraphale was most certainly not human.

"Harry!" the shop-owner beamed. "It's been ages since you last visited, my dear. How are you?" Harry smiled.

"Passable, thanks. You?" Aziraphale made an expression of distaste.

"I had to sell two books last week. Two!"

"Uh, aren't bookshops meant to sell books?" Dean broke in. The look on Aziraphale's face was so scandalised that Dean wondered whether some other comment had accidently come out of his brain instead. Though, come to think of it, the shop didn't really give the impression it wanted to sell anything. Not that that was stopping Sam who was already half hidden behind a bookcase. Dean sighed.

"Sam," he called. His brother poked his head round the corner, then darted back. "Sam!" he tried again. The puppy-eyed look he got was almost enough to convince him, but twenty-five year old Sam had nothing on the pleading expression eleven year old Sam had had. He glared and Sam slowly slouched back to them, casting longing glances back at the books.

"There's a fifteenth century copy of Dante's Inferno! In the original Italian!" Dean sighed again. His nerdy little brother was back in action. He looked up to see that both Harry and the shop-owner were watching them with disturbing twinkles in their eyes.

"So, Harry, who have you brought to visit me today?"

"This is Dean and Sam Winchester. They're hunters." Dean nodded. Sam was a little more enthusiastic, immediately complimenting Aziraphale on his book collection. Aziraphale smiled at him and then frowned.

"Oh dear, the Winchesters?" Harry nodded, a frown on his face too. Aziraphale shook his head slowly, sighing sadly. "I'm sorry to say that your lives look to be getting a whole lot more complicated."

"What does that mean?" Dean demanded aggressively and Sam shifted beside him into a ready position. Aziraphale shook his head again.

"I'm sorry. I can't tell you. I'm on thin ice as it is. In fact, it's against orders to tell you I'm an angel, let alone anything else." Dean scoffed.

"Angel." Aziraphale raised an eyebrow and tried to look superior. It looked wrong on him, somehow.

"You do not believe me?"

"If angels exist, prove it." Aziraphale sighed and two large, white wings unfolded from the space behind his back. A sword appeared in his hand and burst into flame. He didn't spontaneously grow a halo, but he did start glowing with a white light and his eyes could have been used for torches. A humming started and rose in volume until it tore at Dean's eardrums. The humans covered their ears, screwing up their faces. Dean shouted something he couldn't hear. He thought he admitted belief in angels and told the angel to turn 'the damn sound effects off'.

A moment later everything was back to what it had been with the angel looking smug. Dean thought the expression suited him better than the attempt at superiority. It didn't stop him from wanting to punch the book-keeper right in his smirking mouth, though. Dean darted a glance over to his brother, but the boy was star-struck, or, more to the point, angel-struck. He'd be hearing about this for months, the elder hunter groused internally.

"OK, so angels exist. I'll expect the tooth fairy tomorrow and Santa Claus next Thursday," he said sarcastically. "Now, can you give me anything to get rid of a demon or not?" The angel looked a bit taken aback. He looked over to the wizard for help. Harry obliged.

"They've got to deal with what I reckon is a fallen angel. I was wondering if you had some of that Holy water you gave to Crowley lying around somewhere?" The angel looked thoughtful.

"Well, it's no trouble to whip some up if I don't. Which fallen angel is it?" Harry shrugged.

"We don't know," Sam said, finally over his fan-girl moment. "We just know he has yellow eyes and apparently that's not a human-demon colour." The angel's gaze sharpened and he looked almost dangerous for a moment.

"This 'demon' wouldn't happen to have pupils like a snake, would he?" Sam's eyebrows went up.

"No. He doesn't have pupils at all. Just this mustard colour background with bits of white and black mixed in." The angel seemed to breathe a sigh of relief, though why knowing that would be good, Dean didn't know.

"Fine. I can bless some Holy water for you. It should do the trick as long as you get it all over the demon. Best way is probably to use a demon trap. Uh," he seemed to hesitate. "If you do ever happen to come across a demon with eyes like a snake, that is, golden with slit pupils, by the name of Crowley, I would really appreciate it if you gave me a call rather than throwing Holy water on him or exorcising him." He fumbled in the drawers below the counter, finally withdrawing a dusty kind of business card which he passed over to Dean. "Crowley got them for me," he said in an aside to Harry, sounding a bit embarrassed. Dean just shoved his confusion out of his brain. This afternoon was surreal enough. No need to make it worse by questioning.

It seemed like a reasonable enough request, so Dean made a mental note. The rest of the time passed swiftly enough: the two brothers were given a whole five litre bottle of Holy water. Dean would be testing it as soon as they got the chance to make sure they hadn't been given a dud. Sam even managed to convince Aziraphale to part with one of his treasured tomes. Then it was just arranging a flight, putting the inflated ticket price on an unfortunate Mr Liam Peterson's credit card, and saying goodbye.

As they walked through the doors to the airport, Sam grinned smugly at his elder brother.

"So, angels, huh?" Dean glared at him.

"I'm not convinced." Sam rolled his eyes.

"Come on, Dean! The guy sprouted wings. He started glowing. He had a flaming sword. What else do you want?"

"To get laid. And a proper beer," Dean sniped back. Seeing Sam's bitch-face, he sighed. "Look, sure Aziraphale isn't human. To be honest, that just makes him something we hunt. Who says human legends about angels weren't about some supernatural race?" Sam glared at him.

"Demons exist! Can't you just accept-"

"Look," Dean interrupted. "I'm about to get on a hunk of flying junk which could take a nose-dive and become a flaming inferno at any moment. I really don't want to have this conversation with you now. Or ever."

Without waiting for a response, he widened his stride and approached a free desk-attendant. Sam was silent all through the process of getting their boarding passes and the walk to the waiting area. It wasn't until they were almost at the gate, about to board, that he spoke again.

"Blowing up those zombies was cool, though." Dean felt a grin creep on his face.

"Yeah. It was."

*My idea is that Hastur used to be close to Ligur in a rather negative (they are fallen angels/demons after all) way and took offence at his abrupt death. He came after Crowley for revenge but tried to attack while Aziraphale was having tea with his demon. The angel then engaged in battle and smote Hastur while Crowley was distracting him. Or something like that.

The brilliant explanation of Holy water is not mine. I found it in Kita Kitsune's 'Fifth World' and pounced on it (with permission). I think it's a wonderful way to get around the whole Holy water issue. After all, in GO, Holy water dissolves demons immediately, whereas in SPN, it just scalds them. So, how to get around the Holy water issue without making Crowley particularly vulnerable or resurrecting Ligur: make different levels of holiness.