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AN: My first attempt at case work. Eep!

The soft rush late night traffic does nothing to dampen the sound of her sobs echoing pathetically off the cold stone walls of her bedroom. Her chest aches, scars pulled tight against her ribs, neck and shoulders soaked with tears she stopped fighting an hour ago.

She arrested him tonight. For the third time.

This is the first time it's broken her heart.

The look of absolute betrayal he'd worn haunts her, the unspoken plea in his eyes seared into her mind. She wants to believe that he could never do this, that he's not capable of such violence. She wants to think that she knows him better, knows his heart. But does she really? She's seen him attack on more than one occasion, his fists turned to weapons, a gun held in his hand. She remembers his adamance about Damian Westlake, how he was convinced the man wasn't capable of murder. She'd told him that she could make that statement about only a handful of people she's met in her life.

He was once among them.

But now -

The evidence is mounting. A connection with the victim, a hidden past. Jewelry. His fingerprints at the scene. A series of phone calls that he says were work related, the last made within twenty minutes of the estimated time of death. His alibi is shaky at best, paper thin and easily dismantled. No one can vouch for him. He wasn't at home, he wasn't with her. He claims to have been at the Old Haunt, writing in his basement office until well after closing but his staff tells a conflicting story, giving his arrival as a little after nine but claiming that he left between eleven and eleven-thirty. Well within the kill zone.

Beckett hangs her head, her tears slowing, heart rate evening out. He's lied to her before. Lied to them all for months on end. She hates the doubt that sits heavy on her chest but she can't shake it, can't write it off as just a series of coincidences. With a sigh, she stands and walks toward her bathroom, avoiding the mirror as she strips off her day old clothes and climbs into the shower. There's a possibility that he's guilty. She doesn't want to believe it but she can't ignore it.

Either way, guilty or innocent, she has to know.

She goes to the precinct at three. She needs to see him and there's no way sleep will be coming for her tonight so it might as well be now. The desk sergeant nods her through and she wants to scream, rail at him for the pity in his eyes. The chair beside her desk mocks her as she drops her bag on her desk, studiously avoiding her reflection waving across the black screen of her computer. She knows she looks like hell, her face bare of make-up, eyes red-rimmed, hair pulled back into a messy bun. The energy needed to pull herself together was just more than she had to spare.

Her stride falters as she approaches the holding cell, the soft soles of her sneakers silent on the cracked linoleum. She watches him through the bars, his body slumped in the corner, defeat written in the curved lines of his shoulders. It's the smallest she's ever seen him and her heart shatters anew, an uninvited sob catching in her throat. His head jerks up at the sound, eyes immediately seeking her through the shadows.

"Beckett." The word is cold and broken, his feelings of betrayal at her doubt hanging off the sharp edges. "What are you doing here?"

"Where were you, Castle?"

He sighs and pushes himself up off the bench, shuffles slowly across the tiny cell. "I've already told you."

"Tell me again."

"Why? So you can pick it apart? See if I tell the same story the tenth time?" He shoves a hand through his hair, his face sallow in the dim lighting. "It's not going to change, Beckett, because it's the truth."

She stares at him silently, the brick wall cold against her back.

"Fine." Castle leans forward and hooks his fingers through the cage she's put him in, meets her eyes unwaveringly. "I left the loft at nine, got to the Haunt at nine-twenty. I was in my office writing until around eleven-thirty. I had hit a block and decided to go for a walk." His words are robotic and measured, the story one he's told a dozen times in the past twelve hours. "I went upstairs and left through the front door, walked around aimlessly for a while. When I was ready to head back, I decided to go through hidden entrance because I didn't feel like making small talk with the patrons. I wrote until two and then left again through the secret passage. I got home around two-thirty, which you've corroborated with my doorman and the security tape from my building."

"Why did you leave through the tunnel the second time?"

"Why does it matter? You think I did this."

"Castle -"

"Because I like to come and go that way. You know that." He drops his voice, eyes closing in what might be embarrassment or shame and she hates herself just a little bit more for putting him through this. "It's fun. The sneaking in and out is fun."

"Why did you pay cash for the cab? Why'd you throw away the receipt?"

"I paid cash because I had it on me. I threw away the receipt because at the time I wasn't aware that I was going to need to establish a fucking alibi so that my girlfriend didn't suspect me of murder."

"Castle," she hisses, stepping off the wall. "Lower your voice."

He glares at her for a moment and then pushes off the bars, paces back and forth across the cell. "Keep going. I know you have more."

"You bought her jewelry."

It's a statement and her chest aches as the words force themselves out of her lungs. He bought her jewelry. A diamond tennis bracelet. Kate's wrist burns, her skin prickling with the ghostly weight of a gift that isn't hers.

"It was a thank you gift." Castle stops in the middle of the six by eight cell, facing away from her. "She works - worked - for Paula and was instrumental in getting me a better deal on the graphic novels. I bought her the bracelet as a thank you. Nothing more."

"But you dated her."

Castle sighs, turning back around to sit on the metal bench again. He leans his head back against the wall, eyes closed. "We went out a couple of times, yes. Years ago."

"Your number is all over her phone records."

"Again, Beckett, she worked for my agent."

"And she used her personal cell to call you for work related matters?"

"I guess."

His hands are clasped loosely between his spread thighs, his left thumb rubbing tight circles over the back of his right hand. She sways as she watches him, mind caught in the loop his thumb is drawing, her body heating with the memory of how those fingers feel on her skin, the lazy patterns he scribbles on her bare back as they lay tangled together in bed.

"Anything else?" His voice startles her, makes her jump, her knees dipping dangerously.

"Castle, I'm just trying to understand what's going on here."

"So am I." He lifts his head off the wall and looks at her, eyes shimmering with betrayal. "I'm trying to understand how it is that you can even entertain the possibility that I actually had anything to do with this."

"The evidence -"

"Screw the evidence," he interrupts, unrestrained anger in his voice. "Screw the damned evidence. You know me. Aside from our personal relationship," his eyes flash and she has to wonder if that relationship even exists anymore, "I've been your partner for over four years. You know who I am, what I'm capable of. And you know - You know I didn't do this."

"Your prints were in her apartment."

"I've explained that. I was there a few weeks ago for a -"

"Were you sleeping with her?" She watches the color in his face drain away, feels something inside herself break off and shatter. She has to know.

"How can you even ask me that?"

"Just answer." She fights back the emotion, tries to keep her voice even. If she starts crying again now she might never stop. "Were you sleeping with Michelle Brighton?"

"No. I'm in a relationship." He slumps back against the wall, the fight draining out of him in one fell swoop. "Or I was, at least."

"Castle -"

"Don't." He holds up a hand, halting her empty explanations. "Just don't." The hand falls heavily back into his lap and he twists away from her, curves his body back into the wall. "I'd rather not say anything else without my lawyer present, Detective."