I have been wanting to write this for ages, but could never get it quite right. I hope I did alright by you guys.
This is obviously AU and will require us to place Castle and Beckett back in time as Harry Potter was born in 1980 and the Battle of Hogwarts occurs in 1997. The story takes place right before Year 4 in the books when death eater activity is starting up a la the Death Eater Raid at the World Cup so one could say these events occur in '93/'94.
Sorry for the long intro, but sit back, relax, ignore any timeline errors that pertain to the show, and enjoy this AU to the extreme.
The crack startled him awake. There was no mistaking it. His home was being attacked. Shouts and spells rang from the street, and he heard his mother's howls from the parlor below.
The building began to fall around him. Luckily, his wand was never far out of reach. He barreled over to his nightstand and grasped the 11 inch Cyprus with unicorn hair wand immediately calling out a shield charm.
Safe for now, Richard Castle Apparated to the parlor where he could hear his mother screaming in confusion and frustration. Being a Muggle, magic was hard enough for her to grasp when her son would make his toys levitate as a child let alone when strangers outside were killing all in their path with a flick of their wrist and an utterance from their lips. Thank Merlin that Alexis was on vacation with her mother.
He grasped her tight and Apparated yet again to their summer home out by the sea. He regretfully left his mother vomiting in the front yard and Disapparated straight back, ready for a fight.
He took cover in the mews off of the main road. What he saw and heard was reminiscent of what he had been writing about. There were whisperings that those who were still loyal to You Know Who were starting up violence again. Vandalizing government buildings, targeting Muggles and Mud-bloods, and terrorizing the streets. Rick has been reporting on such news for The Daily Prophet, but each case lacked evidence and witnesses, and on top of that he was refused for print. That was often the problem with magical crime - their sore deeds could be wiped away with a flourish. This, however, was most definitely a Death Eater Raid, and Rick was in the thick of it.
Rick quickly assessed the situation. There were a total of three Death Eaters, all donning their traditional masks. Muggles poured out into the street to see what was going on and to escape their burning houses being brought down by spells and curses while the Death Eaters toyed with them.
Seeing this, Rick quickly took action. He approached from behind and struck the nearest death eater with a disarming spell. This, unfortunately, gained the attention of his other two attackers.
The whips of their return spells whizzed through the air, narrowly missing him. He was able to deflect the others clumsily.
He managed to find cover behind a bus stop, but that didn't last long, as his opponents shrunk it moments later. Casting a block, he barely made it behind a trash bin when a godsend Apparated before him and took out the offending witches and wizards with a single spell.
Confident the threat was dealt with, Richard emerged from the garbage bin and looked upon his savior. She was the most beautiful creature he had ever seen and she had just taken out two Death Eaters at once while Apparating out of thin air. He was instantly smitten. That was so badass. And hot!
He was still drooling over the mysterious woman when she turned towards him and began to speak.
"Are you alright?" she asked, concerned for him when he didn't immediately respond. That concern quickly went away, however when she noticed how gobsmacked he was. "Are you alright?" She snapped.
"Hmm? Oh, yes, fine, quite fine," he stammered when he realized he had been caught checking her out.
Kate Beckett was amused at the man before her. His wand was grasped loosely by his fingertips given his obvious distraction with her clad in merely boxers, an undershirt, and socks. He was obviously disheveled having been awoken to this nightmare. He was ruggedly handsome she noted with his striking blue eyes, trussed hair, and chiseled jaw.
Kate shook off her train of thought and got back to her job at hand. These Death Eaters were getting more active, and it was her duty as an Auror to shut them down. Unfortunately for her, this made the fourth attack this month and she had yet to put a stop to the madness. Assessing the scene, she realized the wizard in boxers was the only magical resident in the area.
He shifted nervously under her gaze as she approached him, tucking her wand into her leather coat.
"What can you tell me of this attack, Mr…" she quizzed.
"Mr. Castle. Richard Castle. Reporter for The Daily Prophet and author extraordinaire," he boasted, extending his hand in greeting.
"Mmmm, yes. I recognize the name. You're the "Unfortunate Calamities" writer, correct? In fact, you've been submitting pieces regarding these attacks, haven't you?"
"Ahh," he hesitates, "yes, I've been writing them but the editor refuses to publish."
"This is why, as you can see. The events are true and the Minister doesn't want a panic."
"I would argue the public needs to be informed. Muggles and wizards alike are all being harmed. I am the only wizard on this block. There is no one to defend them. The public needs to be told if they are to be left to fend themselves."
"I'm sorry, did you not just witness me saving your life?" she asked moving into a defensive stance.
"Please," he scoffed, "I was fine."
"You're lucky I showed up when I did. If I hadn't you surely would have fallen victim."
"I am a victim - my home is gone!" he fumed, "and I can fend for myself," he smugly added.
"I understand. Well, as an Auror for the Ministry-"
"You're an Auror?!" He clumsily interrupts, nearly tripping over himself in glee.
"-I am subject to the Minister's orders and he has ordered the public remain ignorant," she explains. She clearly does not look happy about it.
"Oh, well, please don't obliviate me," he pleads. "I would totally forget that I apparated my mother to my summer house to protect her. Knowing me, I would leave her in Hastings for like a year while she panicked about the 'magicians who magicked her son's house up in flames.'"
The puppy dog look he is giving her is so adorable. She probably won't torture him with memory loss. He already knows about the attacks - hell, he reports them. So instead she ignores his pleas and focuses on teasing him. No reason why she can't get some more amusement out of this man.
"You live with your mother?" She needles.
"What? No, she lives with me." He shakes his head.
"Hmm, sure she does." She leaves it there and begins to assess the damage done to the street. Hyde Park Gate has never looked so gutted. She goes about fixing the scene up, the sight improving before their eyes. She notices Castle still in her periphery, watching her in awe. She lets him watch. It's really not that exciting; this is average house witch stuff.
She then gathers the witnesses and apologizes for taking away their memories so forcefully, but she reminds herself that it is in the best interest. No one would believe them anyways, so she wipes their recollections.
Once the scene has been taken care of, and the order somewhat restored, she turns towards Castle who has a look of resignation on his face.
"So, you gonna wipe me down, too? My mother is going to be so pissed," he jokes.
"Not gonna obliviate you, Castle," she concedes and she watched the elation show on his face.
"You wanna whip me instead?" he winks.
"Ugh, grow up," she scolds.
He laughs, "Seriously, though, thank you. She would have made me buy her a whole new wardrobe or something, do you know how expensive her clothes are?! It's atrocious."
She chuckles, "I am perfectly aware, your mother is somewhat of a fixture of the West End, and it's not like you can throw your galleons around at Selfridges."
"Whoa, you follow Muggle theater?" He's amazed. No one in the wizarding world knows who his mother is.
"Of course. My father is a Muggle. 'Bout as Muggle as they come," she muses with a smile.
"And your mother?" he prods, seeing this as a golden opportunity to learn more from her.
It was clearly the wrong thing to ask as her face snaps shut. It is clear the time for playful conversation has come to a close.
"I apologize, that was intrusive," he says genuinely, "I'm a reporter, it's in my nature and I forget to turn it off sometimes."
"That's alright, I'm an Auror, it's in my nature too." She let's it go. He couldn't have known it was a sensitive topic. Especially given tonight's events. She wouldn't tell him that her mother worked in the Department of Mysteries and stumbled onto something far too great. She foolishly tried to foil The Dark Lord's plot and paid dearly for it. The worst part was that she didn't even know who did it; just that The Dark Mark was left behind and that they fled, leaving her mother's lifeless body in Knockturn Alley. Now that Death Eaters were active again maybe she could actually find her mother's murderer.
"Well, this has been a lovely evening, but I should perhaps put some clothes on. I don't want to keep giving you a free show of my muscular, handsome form," he preens.
He thinks he's so suave, but at least it gets her to laugh.
"You might want to find your hysterical mother, too. Maybe explain to her what is going on and get her to be mum on the subject, yeah?" She plays along.
"Right, that too," he smiles.
She has to ask, "Why are you smiling?"
"You didn't deny it," he points out.
"Deny what?"
"My handsomeness," he gushes.
She wishes she didn't ask, but he is, in fact, rather handsome. She kind of hopes she runs into him again sometime. She decides not to think on that thought for too long, afraid she will walk back to him, and instead apparates back to the Ministry.
Richard Castle looks on as the leggy brunette disappears before his eyes. He prays to all that is magical that this is not the last time he sees her.