"Get the father," the doctor says, grasping the nurse's arm. The nurse nods and heads for the door of the examination room.

She hears that they're going to find her husband, but Kate nearly can't register their movements as she dissolves into tears, releasing the greatest pain she's known in a long time.

The autumn leaves light up the sky with a warm glow, their fire dripping to the ground in a breeze still carrying the scent of last night's rain.

Kate has decided to take a walk, and even though Castle should be writing, he's joining her in the name of "inspiration." He knows that she knows that he's tagging along because his wife is pregnant and he's instinctually protective, but neither one of them says it. Neither of them feels like being alone right now, anyway.

They come to the park, their park, and Kate insists on claiming a swing. Castle intervenes in time to wipe the damp away with his coat sleeve, and she can't help but roll her eyes, because it isn't as though she hasn't sat on this thing in the middle of a downpour before. But her clothing is warm and dry today, so she accepts her husband's gesture and watches him take the swing beside hers.

Facing the brightly colored playground allows them glimpses of children who have come out to play now that yesterday's storm has receded. But that isn't what Castle notices most. That isn't the inspiration he finds in the park today.

The third swing is empty. Castle catches his wife looking at it often. He knows the story unfolding in her mind. He always knows.

She realizes she's been spotted, but she only grins back at him, the luminous glow of the life within her shining in her eyes and cheeks and smile. They're going to make their own history together here, a love story even greater than their romance.

Right now, Castle rests on one swing and Kate shares another with the baby in her womb, but someday they'll have a child to bring here. Someday they will take up all three swings.

After they've sat awhile and enjoyed the crisp air, Kate rolls her neck and looks to her husband. "You ready?"

She means ready to go, but—"I'm all kinds of ready," he says.

They head for the loft, following the route that Kate took in a rainstorm not so many years ago, but when they reach the pavement, Kate loses her traction and slides on the slick leaves.

Castle grasps at her, but like the day he saw the glint of a sniper's scope, he's a fraction of a second too late. She collapses to the ground even as he grabs her limbs with everything in him.

"I knew I should've worn my heels," she says, employing the kind of self-deprecating humor that's usually more her husband's fare.

Stoic as she may be, she can't entirely hide her pain from her lover's perceptiveness. He heard her cry out as she slipped, heard her groan with the impact.

But even as her body shivers with the shock of the fall, she looks at her reliably flat-soled shoes and quips: "How do people walk in these things?"

"C'mon," says Castle, his heartbeat settling once he's helped Kate to her feet. "Let's get you cleaned up."

Not yet at the edge of autumn, the leaves have abandoned their branches. Bare trees brace themselves in the wind. They have nothing left to lose. Most of the fallen foliage is as good as forgotten, already raked and gathered and taken away. It hasn't rained, but the chill is enough to have the couple bundled up in their scarves and long coats.

They're walking, arm-in-arm, to the park. It's their first time back since Kate's fall. Castle knows how their story will unfold today.

When they get there, the third swing will be empty. Silently, Castle will lament the little one's absence. He'll take Kate's hand.

She needs to be there, to make it real. To accept what they had—however briefly—and remember what they still do. He'll go because he wants to accept and remember, too, but mostly he'll go because he doesn't want her to sit beside two empty swings. He doesn't want to leave her alone too long with the aching loss inside her.

But when they get there, none of the swings are empty. Four children are playing at the swing set, one eagerly begging for her turn.

Seeing the overabundance of life stops them in their tracks.

"Let's go home," he offers.

She takes a breath as though to agree, but says quietly, "I want to watch for a minute—if that's okay with you."

He nods and says, "Of course." Anything she wants or needs to do to be okay is okay with him.

"Get the father," the doctor says, grasping the nurse's arm. The nurse nods and heads for the door of the examination room, but doesn't move fast enough for the doctor's liking.

Through the tears blurring her vision, Kate sees Dr. Beall nearly bowl Nurse Creasey over, lunging out the door to find Castle and drag him back here.

Kate wipes her eyes and sobs a laugh to the nurse: "I think Dr. Beall's almost as happy as I am."

No sooner does Nurse Creasey agree before Dr. Beall is leading Castle into the room at full speed.

Kate erupts in fresh tears as her husband weeps with joy at the unexpected news and the sight and sound of a healthy fetus on the ultrasound screen. The greatest pain they've had to face together so far has been so real—nothing will ever undo the torment of that experience. The loss and pain may not have been permanent, but they ran deep. But the sudden revelation that the baby didn't miscarry after all is real, too. Their baby is going to live.

Just like Mom and Dad, stubbornly hanging on to any thread of hope and possibility; defying reason and reality just to declare one more triumph for love.

With Castle at her side now, Kate can't tear her eyes away from the screen; needs to speak to the little one whose heartbeat she thought she'd never hear again. "We thought we lost you."

But her husband lightens the mood in true Castle fashion. "Proving us wrong since before birth," he says. "We better watch this one."

The third swing is empty.

But this time, from where Kate sits in her own swing, she can see her son riding spider on Castle's lap, howling with laughter as his father sways them back and forth.

The little guy's legs are too small to propel them, small enough to wrap around his dad's hips without getting pinched in the chains. Someday their baby boy will be too big to share their swings.

But they're all right with that. They'll savor this for now. And when that moment comes—when he's grown?

They'll savor that, too.