Author's Notes:

First off, I want to say a HUGE thank-you to Pskepsilon from the ABC Castle boards for helping me with this story!

This is going to be another full-length story, complete with an odd case of its own, and hopefully reading like an actual episode would.

This one is just my take on the upcoming Christmas episode this season. We're looking to have the next couple of chapters posted in the next week or so, but here's the opening chapter for now:

Chapter One

It's Christmas in New York City. Despite the early hour, people are already walking down the snow-covered sidewalks, shopping bags in hand, trying to make the most of their last-minute holiday shopping time.

At the 12th Precinct, the elevator doors to the homicide department open up to reveal Detective Kate Beckett. It's early in the morning and signs of a restless night are evident on her face. She enters the bullpen and stops dead in her tracks, noticing that the department has been turned into its own winter wonderland. Lights are strung everywhere, glistening off of the garland hung from corner to corner of the bullpen and around the doorframes of each of the rooms. Ornaments and other decorations have been hung from the ceiling. As Beckett slowly glances around the room, she notices her desk, wrapped in Christmas wrapping paper and with a small yet extensively decorated fake tree placed beside her computer. Even the two chairs at her desk have been covered in garland, each with a large cherry-red bow plastered on the back. Frozen in place, Kate is stunned, shaking her head as if she thinks she is dreaming.

Ryan and Esposito notice their partner, unmoving and brow furrowed. They quickly join her. She glared at them as they approached. "Why does it look like an elf threw up on my desk?" She asked, raising an eyebrow accusingly at her colleagues.

Esposito grinned and pointed towards the break room. Beckett looked over and saw the perpetrator gleefully decorating a massive Christmas tree in the back corner of the room.

"Castle?" Kate asked. "I should have known." She added, shaking her head.

"He's been here all morning." Esposito replied, still grinning.

Ryan nodded. "Yeah, he wanted to surprise you."

Beckett looked back at the two detectives, both smiling in response to her steely glare. "Oh, I'm surprised, alright…" She replied dryly as she rolled her eyes.

Kate headed straight towards the break room, where Castle was still busy decorating the large tree. Her eyes glanced up at the top of the doorway before she entered the room, shaking her head again. She started making two cups of coffee.

Castle spun around at the sound, a glowing smile across his face. "So what do you think?" He asked, unable to contain his excitement.

Beckett looked back at him and opened her mouth to reply. She held herself back from making the smug comment she had intended to, instead holding out a cup of coffee for him. "You could probably use one of these." She said, offering him the cup.

"Thanks." He replied, still smiling. Castle took a sip of his coffee and pointed back towards the half-decorated tree in the corner of the room. "Do you want to help?" He asked.

Beckett's brow furrowed as she replied. "Actually, I have a lot of paperwork to get caught up on." She turned and started to walk out of the room.

"Hold on!" Castle shouted over at her, stopping her in her tracks just outside of the door. Beckett spun around, eyebrow raised. "Can you just take a couple of steps back this way?" He asked, trying to hide his grin.

Beckett smirked. "Sure." She said, playing along. She moved back towards the room as Castle walked towards the doorway. She took an extra step into the room and watched carefully as his smile faded into a look of frustration. Kate had to work hard to hold back her laugh.

"That was more than a couple of steps…" Castle started, his frustration now obvious. "Take one step back." He instructed her.

Beckett again smirked and played along. This time, she took one long stride back, putting herself on the other side of the doorway again. When she noticed his dismay, she couldn't help but laugh.

Castle looked up at her, realizing that she knew exactly what he was trying to do. "How'd you know?" He asked, almost pouting. Before she could answer, he rolled his eyes and replied, "I know, I know, you're a trained detective."

Beckett smiled. "You should have hidden the mistletoe on the inside of the doorway." She suggested as she walked away, Castle following closely. "It was too easy to see from the outside."

Castle nodded, as if making a mental note of her idea. He caught up to her at her desk. She fumbled with the chair, deciding how she could go about sitting on it with it wrapped up the way it was. Before she could even decide if it was worth the effort, her phone rang, distracting her from her thoughts. Beckett placed her coffee on the desk and answered.

"Beckett." She listened intently to the person on the other end. "Thanks, we'll be right there."

Castle looked at her and she just nodded towards the elevator, their silent cue. Beckett waved over Ryan and Esposito and the four of them made their way to their new crime scene.

Castle and Beckett walked through the Macy's store, escorted towards the scene by uniformed officers. Ryan and Esposito were already well ahead of them. They spotted the yellow police tape roped around the SantaLand display in the middle of the large store.

"You know, I loved bringing Alexis here when she was younger." Castle reminisced as they got closer to the display. "Until one year, she was only five years old, but she had started to suspect the whole Santa story. I brought her here and she started grilling the Santa with questions. Poor guy." Castle laughed. "He looked a lot like one of your suspects in an interrogation room."

Beckett smiled at the comparison. "Well, I actually wasn't that smart at her age." She laughed. "I believed in Santa until I was ten." Her smile faded slightly. "I guess I was a little more naive back then."

Castle caught the pained look in her eyes and was about to say something when they approached their partners.

"So what've we got?" Beckett asked.

Esposito smirked. "You wouldn't believe it if I told you…" He said, nodding towards the scene.

Beckett and Castle looked over and saw the body that Lanie was standing over, dressed fully in the Macy's Santa Claus suit.

Castle was the first to speak. "I guess someone's getting coal in their stocking…"