The soft pop of air guns and laugh filled war cries fill her ears as she pushes through the tinted glass door, a smile breaking out across her face. The young kid behind the counter recognizes her and gives a quick nod before turning back to the group of teenagers gathered in a semicircle around the desk, their attention focused more on the equipment in their hands than the safety speech they're receiving. Kate moves to the side of the room, her back pressed to wall while she waits.

The kid, Aaron, wraps ups his speech and sends the players off to the locker room, turning to her with a lopsided grin. "Hey, Detective Beckett. You wanna walk on? That last group is uneven so I'm sure they'd be happy to squeeze you in." He leans toward her, voice dropped dramatically. "Especially once I tell them you're a cop. They'd eat that shit up."

Kate laughs and shakes her head. "Not today, Aaron. We both know Castle would never stop pouting if I played without him."

"Though he'd probably enjoy you kicking someone else's ass for a change. What's the running tally now? Like, eighteen to two?"

"Seventeen to three. He cheated last time."

"And you let him get away with it? I'm shocked, Detective."

"It was his birthday," she shrugs casually, hands lifted up. Aaron snorts loudly, his camouflage name badge shaking. "I was feeling generous."

A door opens to her right and a group of paint splattered men come pouring out, whooping laughter and trash talk echoing around the lobby. Kate can't help the giant smile pulling on her lips, the always infectious joy of this place amplified by the emotions of the day. It swirls in her chest, filling her lungs and pushing against her heart. She wants to run after them and join in, let the adrenaline crash through her veins, pushing her into a euphoric bliss. Aaron taps on her shoulder and she turns back to see him holding a face mask and paintball gun.

"Sure you don't wanna play? You've got that look in your eye."

"No, I'm sure."

"Bummer. You know how we all like to watch you slaughter unsuspecting victims." Aaron drops the gear and bends down behind the counter, coming back up with an envelope tucked between two fingers. Kate laughs when she sees the drips of paint on the front, wonders if Castle artfully arranged them himself or they're just a happy accident of the location. "Guess you'll be wanting this then."

Grinning, Kate plucks the letter out of his hand, her thumb smearing across a splotch of green paint not yet dry. "Thanks." She turns away, then spins back, an idea springing to life in her mind. What better way to celebrate an engagement than with a round or two of paintball? "Do you have any spaces open this weekend?"

"Mr. Castle already has a reservation for you guys for Sunday afternoon."

Oh, she loves him.

"Of course he does. We'll see you then?"

"Like I'd miss the chance to watch you humiliate him. I'll be here."

The phone rings and Aaron picks it up, tossing a wave in her direction. Kate raises her hand in response and pushes back out through the door, the cool early evening air sweet in her throat. She finds a bench a few yards down the sidewalk and takes a seat, pulling the letter out. Her green paint thumbprint stains the back of the paper and she pauses, traces her index finger around the edge. She feels silly but the print makes her feel like the letter is theirs, visibly marked by both of them. Her imprint on his words, the basis of their relationship. Sighing at her own romanticism, Kate unfolds the paper, starts to read.

First thing's first: I didn't cheat. It's not my fault you underestimated my ability to be stealthy. You should know better by now, Beckett. I'm always going to surprise you.

The surprise goes both ways, of course. I was an idiot before we got together. I thought I knew you. I thought that after four plus years of observation I had a handle on who Kate Beckett is, on what makes you tick.

I had barely even scratched the surface.

I knew your dedication to the job. Your desire to right the wrongs of the world, to see justice served. I knew your sometimes scary intelligence, how your brain makes leaps that seem illogical and insane even to me. I knew your drive. Your stubbornness and your determination. Your seemingly bottomless supplies of strength and loyalty. Your unwavering faith in the people you love.

I had no idea, though, about so many other things. The way you throw yourself wholeheartedly into the pursuit of pleasure, whether it be carnal or something a little more tame. Your endless patience with my mother and daughter. Your sense of adventure and how you're always willing to go along with my ideas, no matter how crazy they seem to others. (I still can't believe you agreed to let me reenact that running through the woods scene from Twilight. I also still can't believe you agreed to watch Twilight.) That sense of adventure has led us to leave our mark on quite a few New York landmarks over the last year (and I'm not just talking about the ones in which we've had sex) but this place, unglamorous though it may be, has to be my favorite. This is where I discovered that my inner child has a playmate.

I often think about the first time we came here. You were so amped up. I'd never seen you like that before, your whole body practically vibrating with anticipation. I wanted to bottle that feeling up and save it for later because I had no idea if I would ever see you like that again. I was so stupidly in love with you in that moment, watching you strap on the plastic chest protector while you bounced up and down on the balls of your feet, just itching to get out there and start shooting. You were so damn cute and I remember feeling it bubble up in my chest, the need to tell you. You looked at me, your lips curled in that sexy little smile that you get right before you say something biting, your eyes shining with untethered joy; I will never forget that face. Or the words that followed.

"Don't try to butter me up. I love you, Castle, but that's not going to stop me from kicking your ass."

That was the first time you'd ever said you loved me and I don't think you even realized it. It just flowed off your tongue like you'd been saying it every day for years. I suppose, in a way, you had but hearing the actual words - I was dumbstruck. I just stood there while you pulled on your face mask and then sauntered away, paintball gun bouncing against your leg. You did kick my ass that day but I didn't care because you loved me and that was sweeter than any victory could ever be.

And now it's time to wrap up this little journey with one final stop. I'm sure you're famished from all this running around you've been doing so why don't you stop for some dinner? Tell your dad I say hi.

Kate folds up the letter and pushes it into her bag, taking a moment to reflect on the contents. Was that really the first time she told him she loves him? She could have sworn she'd said the words before that day. Part of her wants to be angry at herself for tossing something so important off so casually but she also feels relief that the memory is a happy one, something they can both reflect on without getting mired in the drama and pain of their early years.

The paint on her thumb is starting to flake and she picks at it as she stands and makes her way down the block, leaving bits of her happiness scattered along the sidewalk in her wake.

We're nearing the end and just wanted to take a moment to thank everyone for their amazing support of this story. All the comments and favorites and follows have been so deeply appreciated. The final two chapters will be up this weekend. Thank you all so much.