Disclaimer: I don't own Doctor Who or Castle. I wrote this fic purely out of my own personal enjoyment. And something creative to do. I get bored easily.

This is my first crossover I have ever done. I was never one for crossovers until I read a few Doctor Who ones. That show is perfect for it. I was thinking on writing a DW/Dresden one but I haven't read all of the books and until I finish them, I will wait on that and work on this one. I hope you enjoy it.

Chapter 1 - Something Blue

She stood there in the shop on top of the small pedestal as she stared into her reflection, her breath taken away. Rich chocolate-brown hair cascaded down her shoulders in loose and large curls, the tips brushing just the top of the crystal white, sleeveless dress. Stones trimmed the top and around her waist, down to a 'v' an inch or two below her naval. The silhouette of the dress clung around her curved hips and down, giving her just enough room to walk. She held her hands together in front of her waist, holding an imaginary bouquet. She could see that bright smile from over her glowing face. It felt not to long ago when she was a little girl dreaming of one day walking down the aisle to her prince charming. And here she was in the perfect dress. It made her feel like such a princess. A goddess.

"You look beautiful."

Kate peeled her eyes away from her reflection to the redhead who stood beside her and grinned. "I feel like a princess." The bride-to-be gazed back her reflection. Vanity was never a trait of Kate's, continually staring at herself in the mirror. She just couldn't help it. She feel so confidant in this dress. "I think this is the one, Alexis. I know it is."

"Of course it is, girlfriend! You are gonna knock Castle speechless in that dress." Lanie, Kate's Maid of Honor, stood back as she admired her best friend in that perfect dress. The coroner was so proud of that woman standing there on that pedestal. She remembered like it was yesterday when she egged that brunette to give in to Castle's wiles.

"Absolutely stunning!" Martha beams at her future daughter-in-law. "Uh bup bup bup!" The older redhead patted away Kate's hand as she reached out for the bill in Martha's hand, curious about how much of the budget this perfect dress would actually use. "What did I say about not worrying about the cost, hm?"

Kate rolled her eyes. "Martha, I'd rather not have to investigate your murder if Rick ever heard you say that." As much as she loved the dress, Kate always took issue with spending other people's money. She wasn't even sure about coming to this particular shop. It was completely out of her price range, despite the fact that it was her own fiancé who recommended the designer to her.

"Kate, don't worry." Alexis reached up her fair hand to rest it on Kate's wrist. "Dad wants you to have your fairytale wedding. Which includes your fairytale dress."

"But-"

"No buts!" Lanie placed her hands on her hips. "Imagine the look on Castle's face when you walk down the aisle in that thing." Her full lips curl into a smirk.

"I apologize for the wait." A tall blonde woman walked back from the front of the store. Carol Jennings was her name. She wore her hair up in a sleek doughnut bun down and don a perfectly ironed two piece suit, but her young face was soft and angelic. "Oh! Look at you!" She walked up to Kate in a pair of seemingly uncomfortable pointed stilettos, clasping her hands together. Her well manicured fingers intertwined with one another. "What did I tell you. Jeffery has an eye for bringing out your inner goddess."

"I," Kate hesitated. She really wanted the dress. It was perfect, but she was also fine with a store-bought dress. Then again, she couldn't say no because everyone worked so hard on it and Rick insisted a designer dress. The female detective caught the slight worry in Carol's eye from her hesitation.

Right then, before Kate could finish her reply, the bell from the front store rang as a new customer walked in. "I'm so sorry, Miss Beckett." Carol's brow furrowed, as if expecting a reprimand. "We've been so busy as of late and I've had a no-show and now I'm being completely unprofessional."

"No! No." Kate stepped down from the pedestal. "Go ahead. I need to change back into my clothes anyways. Take your time." She waved her hand at the young woman, who looked close to Alexis's age.

"Thank you. I will be right back, Miss Beckett."

"Please, just Kate." Detective Beckett smiled before calling back to Carol as the blonde headed back to the front. "And I'll take the dress." Kate turned back into the dressing room, leaving the three women who accompanied her cheering. As Kate undressed, with the help of Lanie to unzip the back, she could hear a conversation coming from the front of the shop that piqued her interest some, only because it was a bit odd.

"Hello, sir. May I help you?" Kate could hear Carol's soft voice over a faint whirring sound that suddenly stopped.

"Oh Hello!" replied what sounded like a British man. His tone was rather enthusiastic and voice slightly rough, squeaking just a bit at the 'hello' part. "Agent John Smith, Health and Safety. Just doing a quick scan," he continued, followed by that faint whirring sound again.

"Checking for what?"

"Oh, you know...stuff." The man's voice lowered and trailed off a bit, sounding as if what he was about to say had gotten away from him. "Well actually of particular kind of bio-psychic energy residue caused by prolonged exposure to-"

He was suddenly interrupted by a scream that came from outside the shop. The sound of the bell on the front door chimed again as Kate had assumed both the mysterious man and Carol had run out of the shop. The detective, who had already dressed herself back into her trousers and was buttoning the last button of her top, barged out of the dressing room and grabbed for her purse. She quickly reached out her gun and badge before barreling through the shop to the front, calling back to her friends, "Stay inside!"

Kate ran out through the door, the bell chiming again behind her as he looked both ways. "I thought I told you to stay inside."

"Someone might need medical attention." Lanie replied behind the detective. "There!" The coroner pointed to the right. About a block or two away was a circle of bystanders crowding around something or someone.

"Call for back up!" Kate called out to Lanie, who already had her cell out.

"Already a step ahead of you, girl."

The brunette sprinted down the sidewalk to the crowd. "NYPD. Make room," she stated, holding up her badge and people parted to allow her through. She stopped to look at three figures in the middle of the crowed, one hunched over another that was lying down, presumably unconscious or dead. Both were male. The third was a woman who looked down at the other two with a horrified expression. Kate assumed she was the one whom she heard scream and alerted her to the situation. The man laying down look ragged. His dirty salt and peppered hair was long and disheveled, match with a tangled beard and mustache on his long, gaunt face. Homeless, Kate noted. The other man, the man who squatted over the victim, wore a long, cardboard brown coat that draped over his tall and thin fame, the bottom half spilling down across the concrete beneath him. A pair of legs, covered by blue pinstriped trousers, peeked out from the opening of his coat, along with a pair of bright red, worn Converse. She couldn't see his face, his head turned away from her, but Kate could see his disheveled brown hair in a more styled and purposeful way, sticking up at the top, locks parted a bit from the use of gel and other hair products.

"NYPD! Put your hands behind your head!" Kate trained her gun at the man, who placed his hands up in the air on either side of his head, before they moved behind it, his knobby knuckles fitting perfectly as his fingers intertwined as they rested against his hair. "Stand up and turn around slowly." Kate watched the man closely as he obeyed, standing up very slowly. But before he started to turn around, something outside of the crowd distracted her. Her eyes only glanced at it for a moment before returning to the man, who was already pushing thorough the crowd on the other side and sprinting down the sidewalk. She grumbled. Why do they always have to run?

"Lanie!" Kate called as she ran across the other side of the circle of people, gesturing to the victim before she heard an "I got it" from her friend. The detective ran across the concrete after the suspect, his brown coat bellowing behind him. He was fast, she had to give him that. She wasn't even sure if she could catch up to him. She paused in her running to train her issued firearm at the suspect. "AGAIN! NYPD! Stop or I will shot!" She shouted at the suspect, causing the pedestrians to disperse, giving Detective Beckett and clearer shot. She lowered her gun a bit to aim non-lethally when suddenly the man turned sharply around the corner. Kate swore and sprinted after him again, turning around that same corner to find him a block ahead of her. She pushed her sprint harder, actually gaining up on him.

She was just a few feet from him before the suspect turned around another corner. Kate smiled. She knew her this city like the back of her hand and her perp just ran into a dead-end. She bolted around into the alleyway and stopped, eyes wide. She scanned the entire alley. She looked up the fire escape to her left, the ladder still up and out of reach. She looked to her right and saw a door, boards nailed shut over it. In the back of the alley, she saw a dumpster, in which she carefully and quietly walked up to before opening it wide and training her gun inside. It was empty, fresh after pick up.

"No," Detective Kate Beckett whispered to herself. The alley was empty. She was only a few feet behind him and her suspect just disappeared. She then heard siren in the distance as back up was arriving to the scene of the crime. The brunette backed away and took one last look around the empty alley before turning around and walking back to the main streets. Something gnawed at her as she paused to look back in the alley again, hesitating. She knew she was missing something. Something very important that she didn't want to see. Kate frowned before clicked the safety back on her issued firearm and walked back to the scene of the crime, completely oblivious to the strange blue box that stood in the alleyway.