A/N: Starts with a scene from "Secret's Safe With Me" and continues on through their honeymoon (as imagined by me, myself, and I).

It started with a handshake.

Damn Castle and his eloquence. He turned that simple gesture, the brief joining of hands, into an invitation to fantasy.

The first time it was a kiss.

"This is me," he'd said, "softly touching your face, pulling you in for a long, slow kiss."

She'd smiled and taken up the metaphor.

"This is me, kissing you back, running my hands through your hair."

Now, whenever he took her hand in farewell, he gave her that same meaningful glance before releasing her, and her mind wandered, every freaking time. And he knew it.

(Sometimes they got to act on their fantasies, later.)

Encouraged, Kate decided to try her hand at some creative writing. The next time they shook hands, she slipped him a scrap of paper with one sentence on it.

I'm unbuttoning your shirt and slipping my hand under it, feeling your heart beat under my palm.

When he looked puzzled and started to unfold the paper, she shook her head at him.

"Not now," she said severely.

He gave her a sly half-smile and sauntered off. Five minutes later she got a text on her phone.

My pulse quickens at your touch.

She smiled, but then texted him back.

Next time, on paper, okay?

So the game began. Kate would slip him notes, always on blank paper, always without either of their names. Rick would hand her his pocket pad, ostensibly to show her something on it, but actually so she could tear his note out of it and stash it on her person.

Some days they were more provocative than others.

I want to lure you into the supply closet and kiss you until your lips throb, she wrote.

His response was You push me back against a shelf and pull my shirt open to use your teeth and tongue on my skin. After you escape and I put myself back together I realize you've left a gorgeous hickey on my neck, barely hidden by my collar.

Some days they were more sentimental.

Someday we'll be able to hug or hold hands in front of anyone, she wrote.

Maybe even a smooch or two? he wrote back. We'll find a way.

When Kate moved to Washington, she had enough to worry about with the job and the kind-of-long-distance relationship. Then in the mail one day, she got a small envelope with no return address, a New York postmark, and the initials RC scrawled across the flap on the back.

Her natural sense of caution was reassured enough for her to open the envelope, in which was nestled a piece of paper.

More than kisses, letters mingle souls. John Donne.

When he called that night, all she said was, "I got your note."

"Good," he replied and they went on to talk of other things.

Every few days she'd either send out a note or find one in her post office box. Once he was on his book tour the envelopes would be postmarked somewhere other than New York. The same paper and envelopes. The thought that he carried with him the ingredients for their correspondence gave her delight beyond almost anything else he'd given her.

When she moved back to New York, she almost missed checking her mailbox every day. She'd sublet her place to one of her friends from the academy, and once she settled back in and started unpacking boxes, she started finding notes. In nearly every box.

Welcome home, Detective Beckett. New York missed you.

I look forward to taking these off. Often. (In the box of lingerie, which also contained a pair of his boxers, for some reason.)

These boots were made for walking...over to my place. (In the box of shoes.)

And in the big box of bed linens: We'll wrap ourselves in each other and shut out the world.

Kate was happy to find that the notes didn't stop, even when they were back in the old routine at the precinct. Even now that their relationship was common knowledge in the Twelfth and they didn't have to be sneaky.

"I like sneaky," said Rick, wrapping his arms around her in the back of a cab on their way back to his place.

"Wouldn't want to get rusty on the stealth skills," she agreed.

In the morning there was a note tucked into the pocket of her jeans; she found it after she got to her desk.

Please don't hesitate to practice your stealth skills on me at any moment. Or any of your other skills, for that matter.

She wrote back I need to polish up on frisking and cuffing. You up for it?

His reply was As we speak.

Her next note read Next time? Cavity search.

It was days before he wrote back, and the whole time he behaved more or less normally, though he spent less time at the precinct. Kate had learned not to ask about his erratic schedule and just bided her time.

Finally a note appeared, folded and slipped under the receiver of her desk phone.

Just saw the dentist. No cavities. But you're welcome to search.

She hadn't laughed that loud, in the precinct, in years. Moments later, Castle sat down in his usual chair, handed her coffee, and smirked so insufferably that Esposito told them to "go make out in the closet already, get it out of your system, damn."

The night before the wedding, Kate was staying with Lanie, and when she showed her friend the box full of Castle's notes, Lanie said, "I told you he'd be fun."

Lanie and Martha were in charge of getting the last of Kate's belongings over to the loft after the wedding. The day after Kate and Rick returned from their honeymoon, he had to go report to his publisher, so she had lunch with Lanie, then dinner with Ryan and Jenny (sans baby), and finally made her way home around eight.

She kissed her husband as she passed through his den. He almost managed to pull her onto his lap, but she evaded capture, laughing, and went into the bedroom to kick off her shoes. It was then that she noticed her box, set squarely in the center of the bed, lid open - and the notes were not in it.

"Castle..."

Her tone was ominous; she could hear him get up and come toward her as she reached for the box -

- and found a book. Its cover was some dark fabric, without markings, and it looked hand-made. She picked it up and turned to look at Rick, frowning, but he had that barely contained "look what I did" excitement in his expression, so she opened the book.

There were the notes.

Every last one of them, including a few that had accidentally gone through the wash and were barely readable, some with food stains on them, some with her lipstick. The notes she'd written were interleaved with his own, in chronological order, bits of paper glued to the pages of the book. Right up to the one he'd left her the day before their wedding.

You're unbuttoning my shirt, your palm on my chest, and I lay my hand over yours, the gold bands on our fingers tapping softly, a sign of our unending love, as I bend my head to kiss you on our first night as husband and wife.

She looked up at him with tears in her eyes. He was babbling about not really having to meet his publisher and getting their friends to keep her out all day so he could finish this project and -

She was about to put the book down and go to him when he said, "Look at the title page."

When she did, her tears spilled down over her smiling lips.

Volume One of ?