Disclaimer: My words, not my characters.

Wrote this at the start of season four but hit a wall. I will share what I've written so far (about 20,000 words) but would appreciate any help.

They didn't need words.

The last few days had proven that words helped. And hurt.

But for something as simple as this?

His arm around her back was enough.

You've got my back and I've got yours.

"There is no way we are just going to be able to bring him in here," Esposito muttered, rubbing his hands over his eyes. This case had them all fighting a pounding behind the temples. It didn't seem like a complicated murder. A bike gang member beaten. The problem was, the only people to take out someone like that are usually the same kind of person. Either that or they are very, very stupid. Just because the murder wasn't sophisticated didn't make their job any easier.

Their problem was that no one was going to rat out a fellow member to the cops, whether they liked the vic or not. Not if they valued their own lives. And then there were the rival gangs. In the last two days they had been through more suspects than Beckett cups of coffee after an all-nighter.

Finally though there was a candidate. From the same gang.

"That's what the warrant is for." Beckett sighed, still typing in the required information. She was well aware of how useless this formality was. "That way when he refuses to co-operate…"

"Which he will." Castle added.

"We can drag him in here in cuffs," she finished with a flourish and hit print.

"He won't say anything." Ryan argued.

"We're not going to drag him in here until we have something concrete."

"Which we don't have."

"Planning ahead."

"No one in that gang is going to talk to cops." Espo said.

"Would they talk to some potential new members?" Castle piped up suddenly. Beckett turned to him sharply. Undercover in a biker's gang? He didn't think she was honestly going to let him do that, did he?

"You up for a little undercover work, detective?"

"If you think you can handle it, Castle," she teased.

"Oh, I've got it down."

"Yeah, right," she muttered. He looked injured. "There is no way that is ever going to work."

"She has got a point, bro." Esposito said. "These guys are tough."

"Yeah," Castle said as if Esposito was just stating the obvious, "They're a gang."

"Yeah, Castle," Ryan added. "Even the girls are probably tougher than you."

"Oh, come on." He looked imploringly at Beckett. She would back him up right?

"You're a pansy," she said with a direct look.

The three detectives faced each other and began discussing other options in an attempt not to laugh at his face.

"Hey wait, you have to give me a chance!"

They turned back to him. "I did," she told him. "You remember when we went into the Westies?"

"But we weren't undercover then!"

"And what difference did that make?"

"I wasn't ready! And that pickled onion was something else."

She put a hand on her hips and repeated him incredulously, "You weren't ready?"

"Castle, they aren't going to give you time to get ready," Esposito said seriously.

"What do you even mean, 'ready'?" Ryan seconded.

"Whoa," he held up his hands under their onslaught. "You know what I mean. I mean, like… to get in character."

She rolled her eyes, and turned back to the boys. They looked at his sincere expression for a second longer before looking back to Beckett. 'Get into character'. He was a writer alright.

"No, seriously, wait." He stepped in between them.

"Castle."

"No, I'll show you."

"Show us what?"

"That I can do it."

"How's that?" The boys asked.

"Just give me one minute."

She looked at him, amusement warring with annoyance. She had to admit he looked serious.

"Fine," she looked at her watch. "One minute." Why was it so hard to say no to him?

"You serious?" he asked.

"57 seconds."

"Okay, okay." He quickly shrugged off his jacket and began unbuttoning and rolling up his sleeves. Then he began undoing his shirt.

"Castle," she swallowed. "What are you doing?"

He didn't answer but kept undoing buttons. She was glad the boys were as surprised as she was and were watching him. That way they wouldn't catch the look on her face.

When half of his buttons were undone, revealing a tight white singlet, he reached for his belt.

She snaked out a hand.

"Whoa, there boy."

He looked up into her face, and she couldn't get the rest of her complaint into words before he shrugged off her hand and loosened his belt. She had thought the only one this experiment was going to make uncomfortable was going to be him. How was it he always turned it around on her? From there he shimmied it and his pants down a couple of inches and redid the clasp. He then pulled his now-free shirt down to meet it.

"How long have I got left?"

She just stared at him for a second, before she managed to spit out, "20 seconds." She pulled a random number from her head. She wondered if she should tell him he was channeling the wrong type of gang. From experience, she knew that lowriding was not practical for straddling a bike. Let alone in leather.

He took his head in his hands and rubbed at his hair furiously for a few seconds and then straightened and ran his fingers through it to style it roughly. Then he slumped his head down and closed his eyes.

"Castle?" Ryan asked

He ignored them.

"Bro." Esposito tapped him on the shoulder.

She was fascinated, but trying not to let it show but simply counted down. "5,4,3,2,1."

For a moment he didn't move, but then his head came up slowly. She was about to say something but she kept her tongue as she tested the air around him. She stared at him, trying to pinpoint what was wrong. There wasn't anything major, just little details. His chin was held higher and on a slight tilt, his shoulders were rounded a little more, his stance a little more widespread. But she knew this wasn't the usual Castle. That, and there was a hardness in his face, something in the back of his eyes she didn't recognize.

Esposito and Ryan were similarly speechless.

He cocked his head to one side and smirked. "What? No interrogation? New York's finest. Looks like you've updated the fitness level but lowered the smarts. Tell me, do you guys know what a doughnut is? Repeat after me DOUGH-NUT."

They both blinked.

Still with the same smirk, he swaggered closer. That was the only way she could describe the rolling gait he used to make the few steps. He didn't stop till he was right in their faces, leaning condescendingly over them. She was surprised at his height, though she knew she shouldn't be. She knew his height down to the last centimeter. But now, it was like he was abusing it, pushing himself into their personal space. They involuntarily took a step back and he smirked even more, puffing himself up somehow.

"Castle?" she asked, uncertain for some reason.

He didn't even move his body, his swiveled his head over his shoulder to look at her, with a disgusted look on his face. He shouldn't have to listen to her; a woman. When he saw her though, she saw the look slowly change into a leer. She repressed a shudder. Not moving his head, the rest of his body turned away from the boys until he faced her. This time it wasn't a swagger, it was more of a strut.

Again he didn't stop until he was well into her personal space. It took all of her will and training not to step away from him. You never gave away power. A part of her was surprised because he wasn't even as close as he usually stood. It was like he was a whole different person and she didn't want him anywhere near her. Despite this he stepped even closer and locked his eyes with hers. They were calculating and confident.

"Well, what can I do for you?"

She didn't answer. Couldn't answer. What was she supposed to say? She didn't know who she was speaking to. Not Castle. A witness, a rival gang member, a suspect? She had no information, no leverage.

"Nothing?" he asked. He stepped closer still and took the corner of her jacket. "How about I tell you what you can do for me?" He leaned forward and she could feel his breath against her cheek. He tugged on the corner and she involuntarily stepped forward and collided with his chest. She pushed herself way and felt the heat of him burn her palms through the thin fabric of his singlet. She was also surprised at how hard he was. She knew he was strong, but she never imagined, that under all his button-up shirts, he was this muscled.

He didn't take his eyes off her as she stumbled back. She could feel the shock on her face.

"What's the matter, detective?" He lowered his voice, making it seductive. His stance lost its laziness and he was very still, and his eyes were intent. He remained locked on her face for a full ten seconds before he began moving forward again. She made herself keep the distance and matched him, one step back for his every step forward. Until she hit her desk and he suddenly filled her vision.

He watched her closely, enjoying her reaction, before lowering his eyes to her lips. Taking his own time.

She felt herself trembling. There was the same familiar Castle smell, warmth and blue eyes staring down at her. All of it seemed so familiar. Even the feel of him pressed up against her, and her heart crashing in her chest were familiar on a level she never let herself consciously acknowledge. But at the same time it was so wrong. It was like someone had taken away the essence of her Castle away and replaced it in his body with something much dirtier. There was nothing of the Castle she knew there.

But, she couldn't break away anymore than she could slow her heart rate. Her heart was caught. It wasn't Castle, but the feel of him against her was. She tried to pull herself together. She had dealt with scummy ones before. She usually just put them in cuffs before they even got started. And she never, ever flinched. But she couldn't even manage a word as her heart battled between revulsion and what?...desire?

"Yo, Castle," Esposito called, picking up her distress.

He didn't move his eyes from her face.

She felt herself struggling to breathe, hypnotized by the deep blue.

"Castle!" Esposito clapped a hand on his shoulder and tried to pull him around. Again she got a sudden insight to Castle's strength. Though Esposito had put effort into turning him, he only succeeded in moving Castle's shoulder. It worked in breaking the spell he had over her though. Castle's eyes went hard again and he turned menacingly back on Esposito, moving away from her at the same time, so when he completed the rotation, Esposito's face was practically against his chest. Feeling threatened, she saw Esposito tense himself up too and even Ryan stepped forward, coming to stand close behind his partner, a hand straying backwards to where he had his weapon.

She saw Castle's face come up from where he had been looking down on Esposito, and she thought for a moment he was sizing Ryan up before he just closed his eyes and his neck slumped.

For a few long heartbeats, no one moved. She swallowed, trying to get a hold of herself. By the look of the boys, they were still tense too.

And then his head came back up again.

She saw the boys' guard fly back up, especially when he raised his hands. But he just put them to his own chest and began doing up his buttons. They watched in disbelieving silence, as he rolled down his cuffs and buttoned them. He undid his belt again, replaced the waistband on his hips and tucked in his shirt. He used his fingers to comb his hair back into its usual order then reached past her to snag his jacket from her desk and shrug it back on.

"So," he said calmly. "Do you think that would be good enough?"

They all stared at him. When he didn't get his answer, he looked from face to face, and his brow slowly furrowed.

"Guys?"

She saw Ryan shake his head slightly, as if trying to dispel something. She was still searching for her voice.

"Castle?" He asked.

"Yeah?" Castle raised his eyebrows. "Seriously, what is wrong with you guys?"

Still no response. He twisted around to look at her. She found herself looking up at his warm eyes. All she could read from him was Castle. This was Rick, through and through. But she couldn't shake the memory of his little act. Her heart rate still hadn't returned to normal.

"Ummm…" was all she managed.

"I said I was going to show you I could pull off the undercover." He looked from face to face in appeal. "I thought I did a pretty good job. Is it still not good enough?" He frowned. "Maybe my mother could give me some acting advice…" he broke off thoughtfully then grimaced. "Or not."

As they listened to him ramble, the boys relaxed. It had been a surprise, but any cop that didn't deal well with surprise didn't last long. Soon all she read on her fellow detectives' faces was awe.

"Castle man," Esposito said, breaking the silence, "You are a freak."

"Huh?"

"How did you do that?"

"I don't know. Compartmentalization?" He shrugged. "So was I any good?"

"Good?" Ryan asked. "I seriously thought you were about to deck him."

"Yeah, I thought so too." Esposito joked.

"I wouldn't have actually done it. So what do you think Beckett? Did I pass the test?"

She just shook her head and let out a surprised laugh. "It was like you were a different person."

He beamed at the praise.

It was like he had never gone. How could he do that? Just switch back and forth? She was still figuratively shaking.

He looked at her for a second longer, before he processed something on her face she didn't realize she was showing. His face fell a little.

"Are you okay?"

She shook herself and cleared her throat a little. "Yeah, I'm fine." She gave him a tight smile. "Just surprised me is all."

She tried to blow it off and she mentally told herself to get a grip again, but he still looked a little worried.

"So, Castle is good to go," Esposito said. He swiveled to look at her. "How 'bout you?"

"How 'bout me, what?" She asked flatly as the other two looked at her too. "Oh, come on. You guys know I can pull this off."

They didn't look away.

"You just want me to put on a little show."

They just smiled hopefully.

She just locked eyes with them, but their eager faces never faded. She let out a little puff and rolled her eyes.

"Fine," she said sounding resigned. "But I get a minute to 'get in character' too." At this she shot a sarcastic look at Castle.

"Wait, wait, wait. Lanie has got to see this," Esposito groped inside his jacket for his phone.

"As if I need a bigger audience," she muttered, escaping to her desk. Castle followed and sat down in his customary chair, wisely keeping his mouth shut.