For Julie – Happy (okay, a little bit belated but the thought was still there on the actual day) Birthday!

She walks into the loft holding a bag of Chipotle in one hand and cradling a wet lump of hair in the other.

"I know which one I'm eating for dinner," Castle says, walking over to take the bag so she can remove her soaked coat.

"If I ever decide to get takeout in a tropical storm again just because I have nothing to eat in my kitchen, you can pull rank," she tells him. "Careful," she warns as he takes the Chipotle and reaches out to grab the odd ball of hair that must have some sort of significance.

It lifts its head.

He screams, jerks away, falls backwards, and just barely manages to keep from landing on the bag of food.

Beckett glares. "So help me if you crush the burritos that I risked life and limb to get for us."

"What the hell is that?" he breathes. He can feel his pulse thumping in his toes, chest, stomach, a pounding rhythm that might be slightly irregular. "I think I'm having palpitations. What's the first thing to do for a heart attack?"

"Call an ambulance," she says blandly. "And a hamster."

"Call a hamster?"

The glare intensifies.

He lifts himself gingerly off the floor, careful not to make any sudden movements lest the subtle murmur he swears he can feel in his pulse intensifies into full-blown cardiac arrest. "Why is there a half-drowned rodent in your apartment?"

"I stopped by the humane society on my way to get our Mexican food," she says.

"But it's only three blocks to the –" He stops himself when she rolls her eyes. "Oh. You would be sorry if I suddenly collapsed and your last words to me were grounded in sarcasm instead of undying love."

"You're not having a heart attack, Castle," she says, carefully transferring the animal to her other hand as she shrugs out of her soaked coat herself.

He sidles up to her carefully, stares into her palm. Now that he's expecting it, the thing does look like a hamster, a couple ounces or so of soaked white and tan fur and black eyes, barely slit open, tiny ears and a minute pointed nose. "Okay," he concedes. "It's a little bit cute."

"No. It's wet and dirty and I'm undoubtedly seconds away from full-blown cases of both rabies and salmonella."

"Spoken like every bleeding heart animal rescuer out there," Castle says, walking over to the kitchen to deposit the food on the counter as she toes out of her shoes. He sighs mournfully when he pulls the brown paper bag out of three layers of soaked plastic – the storm had come on more suddenly and more strongly than anyone had predicted, and they'd spent the day cooped up in her apartment, subsisting on peanut butter and crackers and each other. She'd waited until he was on a conference call with the Nikki Heat production team, quietly whispered to him that she was going to find something edible, and slipped away before he could even squeak a protest. He hadn't wanted her out in that weather, but now that the food's here it's criminal that it's cooling on the counter as his stomach rumbles.

She sighs as he emerges from the kitchen. "Saw it lying next to a trashcan on my way back. I tried to call the Humane Society, but of course they weren't open."

"New York in a storm," Castle laments, trying not to beam at her.

She blinks at him. "Don't look at me like that," she orders, walking towards her bathroom.

"Like what?" he asks innocently as he trails after her.

"Like I'm the kind of person who goes out of her way to rescue a goddamn hamster."

He lets the pointed silence hang in the air.

"Don't even say it," she threatens as she turns into the bathroom, lays a clean, fluffy towel out on the counter, and folds the tiny animal gently inside. It looks utterly ridiculous.

"Maybe a washcloth would have been a better choice."

"Look, you wanna do this?"

"Nah. Someone's gonna have to put you in an ice bath to break your salmonella-induced fever."

Her hair is soaked, plastered against her cheeks, and her eyes have a sharp kind of brightness to them that usually means she's seconds away from either getting him naked or maiming him. He wouldn't currently bet on the former.

"I think it's sweet," he says, trying for sincerity.

The look doesn't dissipate. "It was obviously domestic," she responds, giving a rationale he certainly doesn't need.

"You weren't just going to leave her there," he says, consoling.

She heaves a sigh, stares at the tiny animal lying a little bit too peaceably on the towel. "I'm starving. And what the hell are we going to put this thing in?"

Castle whips out his phone. "I heard Ryan talking about this just last week. Didn't Jenny's kindergarten class have some kind of gerbil or ferret or small mammal that just di –"

Her hand reaches out and wraps around his wrist so fast that he almost drops the phone. "Jenny is never going to know about this. Esposito and Ryan are never going to know about this. Nobody. Is. Ever. Going. To. Know. About. This."

Her grip on his forearm is utterly terrifying in its intensity. "Good God, Beckett, it's not like you've shot someone."

"I've shot plenty of people. That's fine. I've never rescued a hamster."

And, okay, he does have to admit that he can already picture the ribbing the boys would give her, even if they absolutely would have done the same thing themselves if they'd had the misfortune to stumble across a hamster in a storm. "Shoebox?" he suggests.

"Yeah," she says, reaching out and gently moving the towel in circles over the animal. It opens its eyes, tilts its head slightly so that it's staring up at her, its nose twitching slightly. The fur's already getting drier, and he can tell it's going to be cute enough from the way it's fluffing up. There's something about the trusting, reverent way it's watching Beckett that plucks a pang of empathy deep in Castle's chest. She's taken care of him before, gently toweled him off after a long day, and if afterwards, someone tried to take him away from her –

"Let's keep her!" he says, the words dragged from him almost involuntarily.

Beckett lets go of the towel, whirls to face him. "No," she says, pushing her finger into his chest.

"She's just a tiny thing. She'll be fine!"

"First off, you have no idea if this thing is a female, so stop referring to it as she. And – and –" she breaks off, throws her hands up in the air. "Just no, Castle!"

He wants to step into her space, but he's pretty certain he'd be losing more than one valuable appendage if he tried it. "Why not? It's not the most unreasonable request I've made of you. Not even in the past week, if you count that time in the shower when I –"

"Don't talk about that in front of the hamster," she whispers furiously.

"Hah!" he says, practically hopping in victory. The hamster stares up at the two of them, blinking sleepily. "If you didn't care about the hamster you would let us talk about all the depraved, debaucheries, del –"

"It's not a cop pet," Beckett growls at him.

He cocks his head. "What is a cop pet?"

"A dog. A cat. A snake. Not a freaking hamster," she grits out, grabbing the corner of the towel and gently rubbing the animal again. It twitches slightly, but it doesn't try to run away, and Castle again feels a lurch of kinship with the tiny thing – it's smart enough to stay as close to Kate Beckett as it can.

"We could name her Burrito," he starts. "No. Too in-your-face. Barbacoa? Except that might give her issues, being named after a kind of meat." He pauses, considers the tiny nose as Beckett steadfastly ignores him. "Tomatillo! In honor of my favorite salsa!"

She stares at him. "Find a shoebox, Castle."

Half an hour later, he emerges from the kitchen with a modified Cole Haan box tucked under his arm. Beckett's sitting on the couch, her eyes at half-mast as she lifts a burrito with her right hand and sinks her teeth into it. Her left hand is occupied corralling Tomatillo, who's making a halfhearted effort to explore the as-of-yet uncharted expanse of Beckett's hoodie-clad stomach.

He holds his creation aloft. "The shoebox is green! Just like a tomatillo!"

"Mft ntff iff nmmf," Beckett says around her mouthful of burrito.

"Oh God, it even sounds delicious, tell me you have mine out here."

She nudges her foot towards the floor next to the sofa, where his aluminum-wrapped holy grail lies. "Unless I get there first. And that's not its name, Castle. Stop getting attached."

He presents the shoebox, nudging it against her elbow. "See?" he says proudly. It's lined with a fuzzy blue washcloth, and there's an attractive little soy sauce dish full of water, and –

"Is that a slice of my last apple? And – popcorn?" She runs a finger absently along the hamster's back. "You'll save us the trouble of fighting over what to do with it."

His eyes fix on her hand, now absently tracing patterns along the side of the fuzzy animal. She follows his gaze, jerks her hand away like she's been bitten. He wisely decides not to call attention to it. "I researched, Beckett. I'm not a moron. I don't want to kill Tomatillo."

"Okay then," she says, scooping the rodent efficiently off her lap and depositing it into the shoebox beside them. It snuffles quietly around the bottom, nosing the water dish before starting to chew surprisingly loudly on a piece of popcorn. "You don't think it could jump out of that thing? I caught John Traichini from 318 beating a mouse to death with his shoe in a stairwell three weeks ago, and I'm not sure your little friend would fare well."

Castle nods toward the kitchen. "I made some holes in the lid. We can put it on when we go to sleep so she won't end up bludgeoned to death." He pauses to unwrap his burrito. "Also, that sounds traumatic."

"Survival of the fittest in the rodent world," she retorts, taking another huge bite of her burrito that seems a little too feral in the context of tiny battered animals.

"Wasn't your tune an hour ago," he says.

Luckily, she's too engaged in her dinner to fully retaliate. "Just wait and see what happens tomorrow morning."

He rests his burrito gently on the coffee table, suddenly not very hungry after all. "You can't just drag her to a shelter after you pulled her half-dead from a sidewalk in the middle of a storm."

She leans over, bumps her shoulder into his, too casually for the pit that's suddenly opened up in his stomach. "I can't, can I?"

"Right," he says, his voice flat. He feels her twist toward him.

His determination not to look at her face lasts for all of half a second. When he glances over he sees a soft, confused smile stretching across her lips. "Why're you taking this so personally, Castle?"

He shrugs, feeling the sudden, ridiculous unhappiness roll through him in a wave. "No reason."

Her eyes slowly map his face. "Castle. I didn't rescue you half-dead from a sidewalk in the middle of a storm."

"You did," he whispers, can't help the mournfulness of his tone.

He jerks his body around to face her fully when he hears her laugh, a full-throated sound that has him staring at her with affront. "You're laughing at me?"

"No," she says, reflexive, her eyes so clear and mirthful that he can't help but return a shadow of her smile, can't resist reaching out a hand and trailing his fingers it down her bicep. "Yes," she says, finally settling down into a teasing smile. "Sorry."

"I was drowning and I didn't even know it and you saved me," he says, the words spilling out of him before he can rein them back in.

She blinks slowly, leans into him, runs her lips lightly over his, curls his fingers at the back of his neck and rests her forehead against the bridge of his nose. "And that's not even a little melodramatic," she murmurs against him, gentler, now, still softly playful.

"Fine," he admits. "Maybe not drowning." He pauses, swallows, not quite sure how to get her to understand. "But Kate –"

"I know," she says. "Me too."

He pulls away, staring at her, sighs. "Sorry for projecting onto Tomatillo."

"Maybe if we take it one day at a time," she concedes. "We'll do a trial run."

They won't, he knows. Their first "one day" will be tomorrow, and the hamster can't live in a shoebox, so she'll need a cage, and they'll have to get her some food that's more suitable than plain popcorn, and he'll need to bring her to the vet to make sure she actually doesn't have rabies or salmonella or some form of hamster pneumonia, and then they'll have to find a corner for her to live, and in the span of twelve hours she'll have wedged her way into their lives in irreparable ways.

He already knows there are some things where one day at a time won't work. Some things where you just have to dive in. And, knowing that, it's the easiest thing in the world to agree.

"One day at a time."