He found her in his study; she was running her index finger over the spine of the first Nikki Heat, and he suddenly realized that to her, there were more. Three-book deal, right?

He wondered-

"Wanna give me the title of the next book?" He was joking, but only partly, because his editor had been shooting down all his ideas, and honestly, Castle didn't like any of the suggestions that had been made to him. Frozen Heat, really? Never in a million years.

Kate turned to him, her hand falling back to her side, a smile curling at the corner of her mouth. "Sorry, Castle. You gotta do this one on your own."

"Not even a tiny clue?" he pushed. Sadness shimmered in the dark depths of her eyes.

"Maybe you're not gonna name it the same, Castle. Maybe it's gonna be a different book."

Oh. "Right," he said, feeling like a complete idiot. He had no idea how to get Kate to explain about Trucho, Rourke, any of it. Pushing her right now felt wrong.

Her face was half in shadows, the light from the living room only touching her temple, her right eye, her cheek; she looked tired, and vulnerable, and so damn gorgeous it made him hurt.

"What will happen to you?" he asked quietly, afraid of the answer, his heart hammering in his chest.

She sighed, gave him that soft, patient look that said, You know just as much as I do. "If I succeed," she answered anyway, "then I guess I'll just cease to exist, Castle. The future version of me will be too different from this."

Something inside him rose, growled, protest and a fierce protective instinct that he just couldn't help. It propelled him towards her. "I don't want you to disappear," he murmured, his throat raspy at the thought. "Kate."

She lifted a hand and cupped his cheek lightly, rose on tiptoe until the softness of her mouth brushed his ear. "I'd much rather disappear than live in a world without you, Castle."

He gritted his teeth at that, met her eyes when she came down; the love pouring out of her, lighting up her whole being, left him speechless once more.

A world without him? That's what this was about. She'd come here to save his life. And she was going to leave just as quickly as she'd come, without even that reassurance that she'd made a difference.

He put his hands around her face and brought his mouth down to hers, hard, kissed her with all the desperation he felt at being left without her, without the certainty, the living proof that Kate Beckett loved him, needed him, wanted him. She moaned against him and her lips parted, the open wetness of her mouth welcoming him in a way that made his whole body thrum.

He pushed her against the open shelves, slid a knee between her legs, hoisted her up; she gasped and then squeezed around his thigh, so hot and delicious he had to close his eyes against the sudden vertigo.

He kissed her neck, tracing the line of her jaw with his tongue, adoring the throb of her pulse with his lips; she arched against him, her hands feverish, jittery over his chest, the mewl of his name ripped from her breathless throat.

Fuck, she was rocking over his thigh and her eyes were closed, the dark sweep of her lashes over her flushed cheeks, mouth open as she panted, worked herself up, so close, so soon-

He quickly worked open the buttons of her shirt, pushed the fabric apart so he could get at her chest; he paused for a split second of stunned gratitude when he uncovered her breasts, nestled in the black lace of her bra, the round scar right in the middle.

He pressed his lips to the puckered skin, heard Kate's whimper above him; he moved his mouth to the right side of her chest, bringing his hand up so he could, at the exact same moment, flick his tongue and his thumb at both tips of her round breasts.

It was all it took. She arched violently and made a noise between a sob and a groan, her body jerking against his, her hips dancing without rhythm in the cove of his hands; he held her close until she had her breath back, until the trembling had eased, and then he pushed a long, certain kiss to her lips.

He wanted her. Kate Beckett. All of her. Now and then, what did it matter? What did it matter?

Her eyes opened, so dark, a little hazy still, but he could see the guilt swirling in them. "Castle," she started, but he cut her off, worked his tongue between her lips.

"I won't ever tell her," he promised against her mouth. "She will never know, Kate. Let us have this, let me give you this."

She shook her head at him, but her hands clenched in his shirt, her head bowing forward.

He brushed his lips over her skin, back to her ear. "You want to change things? Then change this."

She stared at him, so very tempted, he could tell; he could tell how much she wanted him just from the hesitant line of her eyebrows, the dilatation of her pupils, the hands that still lingered on his chest.

He dropped his fingers to her waist, slowly zipped her pants open, and pressed his knuckles to the thin fabric of her underwear, felt the still-pulsing heat underneath. Kate bit her lip hard, but couldn't help the moan that escaped, raw and wanting and beautiful.

Castle slid his hand out of her pants, under her thigh, wrapping her leg around his waist. She didn't fight him, didn't protest; he lifted her up easily, an arm at her back, and made the decision for her as he walked them both to his bedroom.

It was wrong.

It was wrong but oh, it was so good-

And if she could have him now, then maybe that changed everything, maybe her past self would hate him and kick him out for good, and that - that was still better than him ending up dead on a warehouse floor.

She felt his hands slide in the nonexistent space between her jeans and her burning skin, slowly peeling the denim off her, taking his time and teasing the revealed expanse of her legs with his lips, his teeth, driving her wild.

So long, it felt like so long since the last time he'd touched her like this, since-

He licked at the soft skin behind her knee and she arched, growled, so ready, all of her weeping for him, yearning for his touch.

She could hear him chuckling darkly, somewhere far away; but there was delight in the sound too, and breathlessness, and she was reminded again that this was their first time for him-

She closed her eyes, so tight, tried to work up the strength, the courage to push him away, tell him no, no, Castle, you have to wait for her; but even as the words trembled in her throat, even as she tried to figure out a way of pushing them past her lips, he was shucking her pants and her socks, getting rid of his own before he lowered himself to her again, hips meeting hips and chest meeting chest, and the burn of pleasure wiped her mind blank.

He kissed her slowly, thoroughly, running his tongue over the seam of her mouth before he pushed inside; and just that, the wet glide, the low, humming sound he made, that was enough to leave her keening, sobbing for more into his neck.

Her hands were curled at his waist, the smooth, firm skin, sliding up and down under the shirt he was somehow still wearing; Kate's fingers fisted on the fabric, wanting to yank it off him, but his arms were otherwise occupied, were in the way.

She moaned in frustration and tried to push him off her, but he was too solid, wasn't moving; his lips only curled into a smile at her collarbone, and his tongue licked a slow trail down to her breasts, hands brushing against her abdomen, making her gasp, making her forget.

When he reached the line of her underwear-

She felt his teeth against her skin and her hips bucked, irresistible, her whole body flaming up, the need so dark, so heavy in her veins. Castle-

He laughed and abandoned her, his mouth, his hands deserting her; her eyes flew open in incomprehension, something like fear tugging at her heart, but he was only pushing his open shirt off his shoulders, eyes burning into her as he did.

Only his boxers left now; Kate avidly drank in the sight of him, all young muscles and narrow waist, his eyes no longer blue, only the dark pull of desire in them. "You're beautiful," she said, couldn't help herself, and the expression on his face changed, softened by surprise, and then the burst of feeling in his gaze.

He dropped back onto her, the brutal encounter of skins making her shudder, and kissed her ear, her jaw, her neck. Her mouth. "Kate," he breathed, and shit, no, this was not the way, this was only going to make her cry-

She distracted him by hooking a leg around his thigh, pressing herself to his throbbing heat; he groaned and shifted, pushing down, and she had to close her eyes against it, so good, so good, too much.

Too much and she couldn't-

She felt him tugging off his boxers; her fingers traveled down, met the soft skin of him, making him growl against her neck. She stroked gently, turned her head to brush her lips over the curve of his cheek.

His fingers slipped through her heat, friction and tightening need, and then his head dropped, a trail of his mouth moving down. She gasped and arched, tried to cradle his head and pull him away, telling him in a desolate whisper, "Don't. Leave it."

His body shivered at that - her words or her voice, she wasn't sure - and he pushed himself up on his forearms, met her eyes. "What?"

"Don't-" oh god, he was making her say these things, and it wasn't like she had ever had any issues with letting him know what she wanted, but now she felt a strange sense of self-consciousness as he stared at her, this younger Castle... "Keep it for her," she said finally, her heart breaking in her chest. "Not me, not now. Save it-"

He looked into her, eyes so dark, so serious, so intense, and he leaned in close, brushed his lips to her cheekbone. "You don't want my mouth on you, Kate?" he murmured, the words burning their way into her, her hips coming up without her say.

She pressed her lips together, held back a sob, held back her instinctive answer - yes, yes, your mouth, everything, please - and shook her head instead. "No," she managed to spit out, wasn't sure how. "Not - no. Just. Use your fingers, use this-" Her hand closed around him.

He growled, the sound so threatening and delicious against her skin, and he kissed her roughly, more teeth than tongue, his body hard and heavy and everything she wanted.

"I'll use whatever I fucking want," he told her, and he rocked his pelvis against her, making her cry out, need breaking over her in waves, pushing her up into him.

And then his fingers were at her breasts, feather-soft, then harder as he pushed his thumbs against her nipples; his mouth was sucking intently on her pulse point, making her shudder in time with his exhales, her body coiled in one long thread of want, so sharp she didn't know how she was still breathing at all.

She didn't even feel him take off her underwear; she only knew when she felt his fingers pressing down into her wet heat, ragged sounds ripped from her throat, all of her at his mercy, desperate for release.

"Castle, Castle, please-"

He took his fingers back, gave her his mouth instead, making her moan, making her sob, making her writhe until she came, frenetic and breathless and adoring, breaking apart around his tongue, his touch.

When she could feel again, he was right there, so hard, pressing against her; she bit her lip, unable to look away, her eyes trapped in the intensity of his. "You didn't want my mouth on you, Kate?" he asked again, voice so dark, so rough she could have come just from listening to it. "You want this instead?"

He rolled his hips against her, slowly, the tip of him sliding over her wet, sensitized flesh; she clamped her teeth to keep the sounds inside, the pleading, begging gasps that hammered against her chest, demanding to be let out.

He was merciless. He kept going, unrelenting, kept teasing her, brushing the length of him between her legs until she couldn't take it anymore, until she was on fire, inside and out, all of her consuming for him, until nothing else mattered-

On his slide down, she pushed herself up, rolled her hips at just the right moment; he half sank into her, gasped in shock when she used her leg to squeeze around his waist, bringing him down so she could have more, all of him, now.

He pressed down, hard against her, swearing into the soft skin of her shoulder, his body completely still as he adjusted; but she was raw and so far gone, way past ready, and she wanted him moving.

Kate grounded her right arm into the mattress, used all her strength, all the points of contact between their bodies to roll them over; Castle yelped, his eyes shut tight, and she smirked in pleasure when she realized how close he was, how it wasn't just her, but him too, both of them, lost in this together.

And she was on top.

She sat up, legs on either side of him, moaning when the angle changed and she could feel the sharp, pulsing length of him inside her; Castle was panting her name and she lifted up, held his eyes as she slowly, slowly came down again, came down until he was completely buried inside her.

"Kate," he whispered brokenly, and she did it again, so good, so good, she wanted to kiss him-

As if he'd read her mind, Castle pushed himself up, an arm thrown behind him for balance, the other coming around her waist, bringing her to his chest as he crashed their lips together. She kissed him deeply, drowning in it, fingers tightly wound into his hair as her hips pushed in close, rolled away and then sunk in close, their bodies merged, her blood singing-

And then his hand shot down, found her, the press of his thumb and his teeth at her breast, and she was gone, mouth open at his neck as she keened desperately, everything out of her control, her hips jerking again and again and again, endless, his body tense and there and perfect, her mind crowded in dark, exquisite pleasure.

She crashed into him, boneless, the feeling of his hands over her vaguely registering at the edge of her consciousness as he cradled her to his chest, let them both fall back against the mattress; she curled into him, too exhausted to move, to do anything else but breathe against his skin.

"Kate," he murmured at her temple, and in the satiated blur of almost-sleep, she thought that maybe, maybe by giving him this, she had made sure he would stand with Beckett when Kate was gone.

That he would never give up, never relent in his pursuit of her.

She hoped, maybe, maybe something good would come out of the terrible, beautiful thing she had done.

"Don't give up on me, Castle."