Inspired by the spoiler article released about 5x06 so minor spoilers ahead. - A woman from Castle's past shows up murdered, and all the evidence points towards one suspect. Castle. Our favourite writer has a perfectly solid alibi, but can't use it without blowing the lid off his budding new romance with a certain Detective.

I am aware that the brilliant Dmarx beat me to the punch with this idea, although their story is intended to be a light funny one, mine is going dark and angsty. I may even do the whole case if this is received well.

Disclaimer: All Castle characters belong to A Marlowe, if the wait for S5 wasn't killing me so badly I wouldn't have to take his characters out for a spin.

Enjoy :-D

Fingerprints & Pantyhose

Kate stretched as the morning light filtered in through her bedroom window. She had that grin on her face that always came when she remembered that she wasn't sleeping alone. It was Sunday morning and Castle had stayed over last night. She rolled over and found him lying on his back, sound asleep. She draped her arm around his middle and snuggled her head into his chest. Their relationship was still new and exciting, and so far they had managed to keep it to themselves. They stayed at her place more often than his loft as there was less chance of Castle's mother or daughter stumbling upon their tryst accidentally. The newly loved-up couple had managed to keep their romance under wraps for the last month and a half and Beckett still wasn't quite ready to reveal it to anyone yet. She felt a hand sneak around to her hip and run lightly up her spine.

"Mmm…..good morning Castle." She shivered lightly against his touch.

"Morning Detective, sleep well?"

"As well as can be expected given I'm sharing with a man that hogs the sheets." She teased.

"There's a much larger bed at my place you know."

"There's also running the risk of your mother finding out about us, she's almost caught us once remember."

"Would it really be that bad?" Castle paused for a moment and then added, "Wait what am I saying?" quickly changing his mind.

Kate just grinned at him and leaned in for a kiss when her cell began to ring. She grimaced in frustration as she pulled away to retrieve it from her bedside table. Castle grabbed her around the waist and pulled her back into the middle of the bed. "Don't answer it, they'll call back." He latched onto the curve at the base of her neck and her shoulder blade, kissing gently.

Moaning Kate used all of her strength to pull away. "It's the precinct, what if it's a body?"

"Then they'll call back." He repeated. This time Castle pulled her and flipped her onto the mattress so that he was above her.

"Castle….." She protested weakly. He moved down between her legs using his mouth to change her mind. "Castle!" She gasped this time and for the next fifteen minutes her phone was forgotten.

Twenty minutes later Castle's phone began ringing and since Beckett had ignored hers he chose to answer it. Kate was spread out on the pillows recovering from Rick's distraction and he kept one eye on her as he answered it, amazed at the early morning glow she was giving off. She was gorgeous.

"Castle….Oh hello Ryan… A body? You can't get hold of Beckett? How strange, why don't you give me the address and I'll meet you there?" "Mhmm, mhmm," He murmured as he wrote down the address, "I'm sure she'll call you back, she's probably in the shower." Beckett threw a pillow at him.

"Ok Ryan, I'll see you there soon. Bye" Castle hung up his mobile.

"See, I told you it was a body." Kate scrambled out of bed and ran for the shower.

"Hey Kate," He called after her; she poked her head back around the door frame.

"Hadn't you better ring Ryan?" He grinned at her cheekily while holding up her phone.

Kate sauntered back over to him and snatched it back out of his hand. She glared at him as she hit the number into her phone. "Ryan? Hey sorry, I was in the shower….."

When she was off the phone with Ryan Kate hit the shower first, as it would take her longer to get ready. She was dressed and had her makeup on as Castle emerged from her bathroom in nothing but a towel. She kissed him hastily on the lips. "I'll see you at the crime scene."

"Still not driving in together huh?"

"Then who would get my coffee?" She teased.

"You know we're going to have to tell people eventually though?"

"Castle, can we not do this now?" Kate sighed. "Look I'll see you there." She turned, grabbed her bag and was out the door before Castle could protest. He shook his head and moved to the dresser to find some pants. He was amazed he had gotten as far as keeping a drawer at her place; at least that was something.

Kate had met Ryan and Esposito at the crime scene and had gone in to find Lanie overlooking the body. They were at an apartment block only twenty minutes' drive from Beckett's. The victim was in her early thirties, blonde, very attractive and had been found strangled in her bed. They wouldn't know anything else until forensics had gone through the apartment. The Vic had pantyhose tied around her neck, which would make it hard to pull prints. Lanie said that using pantyhose to strangle the Vic was almost as good as wearing gloves. The three detectives went back into the hallway so they could begin canvassing the neighbours. They found Castle walking up the hallway towards them holding his usual two cups of coffee. He was looking slightly uncomfortable and Beckett couldn't place why. Castle had pulled up outside and checked the address twice to make sure he was in the right place. He greeted the three of them nervously and handed Kate her coffee.

"Thanks." She smiled at him. "Rough night Castle?" Even though she knew exactly how his night had been she wanted to account for his odd behaviour now.

"Yeah, I didn't get a lot of sleep." The corner of his lips twisted up trying to hide a knowing smirk.

"Are we going to stand here all morning or do you want to come see the body?" She pushed him as Esposito and Ryan walked down to start canvassing at the other end of the hall.

"Yeah, who is it?"

"A female in her thirties, we haven't managed an ID yet, this isn't her apartment from what the uniforms can tell. All of the bills are addressed to a Mr L Pritchard. She was found by the maid." Beckett told him as they walked through to her bedroom.

When Castle saw the body he dropped his full coffee cup onto the carpet, it spilling everywhere.

"Castle!" Lanie scolded. "Watch what you're doing. If there was evidence in those carpet fibres there certainly won't be now."

"I'm sorry, look I need to step outside for a minute, get some fresh air." He turned briskly and walked back towards the hallway. Lanie looked up at Kate for an explanation and all she could do was shrug in confusion. She signalled with her hand that she was going to follow him.

When she got outside Kate found Castle leaning over the stairwell banister and taking deep breaths.

"Hey…Castle what's wrong?" She ran her hand over his back, trying to sooth him.

He stood back upright trying to act as normal as possible. "Nothing, just a headache, I'll be fine in a minute."

"If you're sure…" Kate wasn't buying it for a minute.

"Look Kate….there's something I need to tell you….." He had to come clean with her before it came out during the investigation, but was interrupted by Ryan and Esposito who had walked down to them.

"Neighbours didn't see or hear a thing." Ryan interrupted.

"We can't do much more without an ID. We should head back to the precinct and start working on a time frame. Lanie estimates time of death between two and four am." Esposito added.

"The woman's name is Kellie Donnelly." Castle told them.

Kate's head whipped back around to him suddenly. "You know the victim Castle?"

"Knew." He corrected. "She's dead."

Esposito's eyes narrowed. "Yeah, we got that part bro."

"She's a friend of a friend. We used to run in the same circles." He went on to explain.

"Were the two of you close?" Ryan asked.

"I haven't seen her in years."

"Ok well we need to get back to the precinct and see if we can track down this Mr Pritchard while Lanie looks over the body in the morgue." Beckett instructed. She began walking down the stairs ahead of everyone leaving the three boys to follow behind. As soon as Beckett was alone in the car with Castle she was on him within seconds.

"Alright Castle; spill; what aren't you telling me."

He rubbed his hands over his face in utter frustration. "I tried to tell you upstairs." He sighed and tried to steady his voice. Kate could see he was fighting some sort of inner struggle, was he trying to work out how much or little to tell her? She placed her hand on his leg to reassure him that whatever it was, it was going to be ok.

"The L in L Pritchard stands for Luke. Pritchard was the other man….Meredith was sleeping with when she was married to me. When I ended it with her she shacked up with him but it turns out when she was a free woman sleeping with her didn't have the same appeal and they broke up a few months after. He started seeing Kellie soon after."

"You kept tabs on who he was dating months after you split with Meredith?" Kate was confused by this odd behaviour.

"Kellie and I were friends from college. We lost touch when she started seeing Pritchard, even though I warned her what he was like."

"Castle I'm sorry. If you're too close to this case I understand if you want out."

"Not a chance, I want to catch this guy. I'd put my money on Pritchard, I say we start with him."

"Rick…." She warned, "You know personal vendettas can't come into this. We'll start with Pritchard because the Vic was found in his apartment. We need to establish if they were still seeing each other."

It was a gruelling first day on the case. Beckett decided to keep Castle's information private unless she decided that it became relevant. Pritchard arrived home after the detectives had left and was met with the uniforms that brought him in for questioning. He had been at the gym all morning. Beckett interviewed Pritchard with Ryan sitting in as opposed to Castle who waited with Esposito in the viewing room behind the glass. Pritchard was the same age as Castle, the same physical build. He wasn't exactly on the unattractive side either. She could see why Meredith might have been drawn to him. He was a lawyer, too which meant he could offer wealth and stability, much like Castle.

"Ms Donnelly was found in your apartment Mr Pritchard, were the two of you in a relationship?"

"She would sleep over, yes."

"But the two of you weren't exclusive?"

"We were together on and off for a few years. Our working life made it difficult to maintain a healthy relationship. She was interning at my firm. Then about five months back we bumped into each other at a local bar, hit it off, but we'd only meet up every few weeks or so."

"Was Ms Donnelly satisfied with your arrangement?"

"She wanted more, kept telling me that we should have tried harder when we were together."

"But you didn't?" Ryan interjected.

"Want more? Hell you've seen her, Kellie was gorgeous, but hey, I've been around the block a few times, I'm not ready to settle down yet."

Castle pounded his fist against the table in the viewing room angrily.

"You ok Bro?"

"This guys an ass." He replied. "He can't see what's right in front of him."

Esposito raised an eyebrow but before he could ask Castle to elaborate an Officer entered and handed Esposito a Manilla folder.

Back in the Interrogation room Beckett kept grilling. "So if Ms Donnelly was sleeping in your bed last night, where were you? Specifically between the hours of two and four am?"

"Kellie and I had been out drinking, this place called The Old Haunt."

Beckett blinked; they had been in Castle's bar.

"We had an argument early on, about six I think. I left her with some friends and me and the boys moved on to another bar. We stayed out partying till about five am and then I crashed at one of their apartments. They'll verify it for you, his name is Jake Fitzgerald. I borrowed his gym clothes this morning and went straight there. Came home and the cops told me Kellie was found in my bed. I don't know anyone that would want to hurt her; you've got to catch this guy." Pritchard was getting visibly upset by this stage. He might not have wanted to commit to the girl but it was evident he cared about her to some extent.

"We'll need you to wait here until Mr Fitzgerald can verify your story, but if it checks out, you're free to go. Oh, and we're sorry for your loss." Beckett added. Her and Ryan stood up and left the Interrogation room, moving into the viewing room just as Esposito was thumbing through the pages of his Manilla folder with a concerned look on his face.

"Is that lab work back?" Ryan asked.

"Yeah it is." Esposito handed the file to Beckett. "You may want to look at this."

Beckett read down the page thoroughly before looking up at Castle. Esposito was staring at him too. Ryan peered over Beckett's shoulder to find out what was so interesting and it wasn't long before his gaze was also focused on their friend.

Castle was puzzled by the way they were all staring at him. "What is it?"

Beckett swallowed before she could open her mouth; her throat had gone bone dry. She tried steadily to hold her composure. "Care to tell us why your fingerprints are all over the crime scene Castle?"