He awakes to the semi-darkness of his bedroom, instinctively sweeping an arm out to the other side of the bed only to brush against cool, empty sheets. Grunting, he sits up to rub the heavy feeling of sleep from his eyes, casting a glance around the room to find the dark shapes around him still, the bathroom dark.
He pulls back the sheets and quietly creeps out into the living room, the light from the Christmas tree bathing the entire room in a soft gold and illuminating the silhouette of the detective standing with her back to him.
"Beckett?" His voice cuts through the silence but she doesn't flinch as she slowly turns to face him, and his comment about her spidey senses is halfway out of his mouth before he sees her tears, the soft light reflecting off the bright shine in her eyes.
He stumbles across the room slower than he would like, sleepy limbs a step behind his brain but he manages to catch her with one hand at her bicep, the other curling around the back of her neck to tangle in her hair. She closes her eyes and leans her forehead against his arm, taking a deep breath, her green eyes brighter when she opens them again.
"Santa came." She motions to the stockings hanging from the makeshift fireplace, leveling him with a look and he can't help but grin. She had asked him if he wanted help putting gifts out after Alexis and Martha had retired to bed but he insisted that he didn't know what she was talking about, that Santa would come later, and had waited until she fell asleep to come set everything up.
"Looks like it," he says slowly, "but that's no reason to be upset. I'm sure there's no coal in there, I think Santa was able to overlook how naughty you've been this year."
A tinge of pink appears in both cheeks and she laughs, palm colliding lightly with his shoulder.
"I'm okay," she says before he can speak again, a half-hearted smile curling at the edges of her lips. His hands coast down her body, coming to bracket her hips.
"And you didn't actually have to wear these pajamas, you know," he continues as if she hadn't spoken, thumbs sneaking under the elastic waistband of the pink, snowman-patterned fleece pants, snapping them against her hipbones. "I won't tell Alexis. The ugly-Christmas-pajama-swap-tradition can change this year too. In fact," he grins, pulling her hips flush against his. "I'll even take mine off in solidarity."
She laughs even as she rolls her eyes, head tilting back towards the tree and his breath catches as he watches the twinkling lights play over her face. He squeezes his hands at their place around her waist and she rights her head again to meet his gaze.
"I wish she could be here too," he ventures, feeling her sigh in response, a shaky thing that rattles through her body as she ducks her head to tuck herself beneath his chin.
"I'm happy," she says quietly into the undershirt he's wearing. "I'm so, so happy. She would have loved you, Castle."
"Maybe not." He snakes a hand around to rub at her lower back. "You don't know what she would've seen you pull out of that stocking in the morning yet."
She jerks back to look over at the the row of red and green stockings, just now seeming to notice the fourth one bearing a 'K.' Her expression is one of surprise, indignation, and gratitude when she turns back to him and he smiles sheepishly.
"I know, I know." He shakes his head. "But I wouldn't be me if I wasn't prepared."
"A regular boy scout," she murmurs, leaning in to lightly press her lips to his.
"Hm, yeah," he breathes into the air between them, lingering a moment before stepping away. "Come back to bed?"
"I wanna stay out here for a little longer." She motions toward the tree but he steps back into her space, grabbing her hand.
"Come here then." Tugging her to the floor, he lies down with his head on the tree skirt and she laughs.
"What on earth are you doing?"
"I saw it on an episode of Grey's Anatomy," he says, motioning her down. "Come on!"
He hears her disbelieving huff, a mutter that sounds something like of course you did but she's shimmying herself under the tree with him, plenty of room between the floor and the bottom branches now that the mountain of presents have been unwrapped.
She hums, blinking a few times as she looks up through the tree. "Those promiscuous doctors might have been onto something here."
He turns toward her, eyes lighting up. "I knew you watched those episodes I save-"
"Don't ruin it."
They lie there in silence for a few minutes, their own personal light show flashing around them before she rolls onto her side and lightly touches her fingertips to his cheek, turning his face towards her as she presses her lips to his. She nudges him with her foot until he turns over to meet her, palm sliding up her cheek to engulf her jaw as the kiss deepens.
She pulls back momentarily, breath coming in rough pants as she glances towards the upstairs level but he can't focus on anything other than the urge to capture her kiss-swollen bottom lip between his teeth, swallowing the groan that rumbles up out of her chest as he rolls them over, just enough room under the fir to press the length of her body into the floor.
He works at the buttons of her pajama top, slowly popping each pink disc as his mouth follows the progress, sliding down and pressing an open mouthed kiss to skin under her belly button. Her muscles jump under his touch and he glances up her body, the heavy rise and fall of her chest mesmerizing, his fingers grazing hot skin as he watches the shirt fall away.
The thin cotton of his own Christmas pajama pants is doing nothing to hide how much he wants her when he crawls back up her body and she arches into him, leg twining around his waist, melding their bodies closer together even as her hands work to get between them. She pushes at the elastic waistband, using her toes to help shove them down his legs and he involuntarily jerks into her palm when she takes him in hand. Their limbs become a tangle as he works at divesting her of her own pants before sliding into her, leaving her pinned by the twisted fabric around her knees.
"God, yes," she whispers and he presses his forehead down, body thrumming as he holds himself still over her.
"I knew it was the pajamas," he gasps and finally moves, hips starting a slow rhythm as she lets out a strangled laugh.
"Shut up."
He closes his mouth around a nipple in response, and her groan reaches his ears as he feels her hands scramble for purchase on his body. He ignores her jumpy movements, slowly rolling his hips into hers, watching the lights dance across her closed eyelids and highlight the flush creeping up her chest. Everything he wants to say is caught in his throat, gratitude and wonder and hope all wrapped up in one but he picks up the speed of his thrusts instead, lets his body speak the things he doesn't dare say out loud, pouring it all into her open mouth.
"Thank you," she suddenly breaks away, eyes wide, and it vaguely registers in the back of his brain that she looks like she's surprised herself by speaking but then she's pulsing around him in a devastatingly perfect way, the flutter of her eyelids the last thing he sees before burying into her neck and losing himself with a hot exhale against her skin.
(It's not until later when they're lying in bed that he wonders if thank you was really what she meant to say at all.)