The air was finally warming and the days growing longer, shadows lengthening to form giants playing across the grass as the sunsets clung on to the city, clutching at the skyscrapers as though fearful to leave, then rising again the next morning with rested pinkness, relieving the silver moon of its night watch accompanied by a churning ocean of stars. The grass grew greener and bluebells broke out like schoolchildren running from their daily prisons at the beckoning cry of the bell, exploding through the woods in central park and filling Fifth Avenue was a hue so vibrant that even the men in suits walking to glass buildings with marble atriums at five A.M stopped to appreciate their brilliance as they took off their coats, finding the breeze tepid enough for shirts and jackets. The cherry trees exploded and it was snowing all over again; this time crystals of dusty rose plagued the streets and kissed windscreens and children played but did not fall victim to the icy slicks which had long ago melted.

On this particular Monday, so brilliant that the sun shot rainbows from the ripples beneath Bow Bridge and green began to shoot from barren branches and siege every birch and oak in clouds of pigment, Richard Castle rose early, welcomed by a sunrise so beautiful it was worth the closure of his dreams, through which the mirage of a woman beside him drifted continuously, never freeing him from the swelling of his own heart or the tickling of butterflies deep in his belly, much to his relief – he never wanted to be free; he never wanted to have to cross off the first item on his bucket list, at least not until all the others were crossed off and he sat in an armchair surrounded by teacups and Sudoku and a puff of grey hair.

Reaching for a cupboard, Castle took out a fresh vanilla pod and scooped out just a quarter of the midnight mud inside before stirring it into a jug full of latte, which he then divided between two pristine white cups with saucers on which he placed three chocolate hearts, thereafter dusting a little hot chocolate powder over delicate white foam to form a fourth chocolate heart, rich and roasted in colour.

Shuffling back into his bedroom, Rick woke his sleeping beauty with a gentle kiss until he felt a smile and his lips touched morning-soaked teeth. She sat, tendrils of gold flowing down her back in tender waves, and stretched, glowing skin radiating the wonder of the sun, and then leaned across to kiss him, soft lips nothing short of rose petals, ethereal in touch and taste and smell. Her eyes at last opened to reveal entire earths trapped behind perfectly polished glass, with rocky hues and grass greens and flecks of honeybee shining through.

Kate Beckett, the unrivalled queen in his writer's world.

They sipped in silence, simply smiling and holding each other's gaze, and when they were done and had allowed chocolates to melt on tongues, Kate fell back into Rick's lap and looked up at him, her head resting comfortably in the dip where left and right married, her cool ear pressing against his scarred knee. He reached out and slid his hand through her hair, catching the sunlight streaming in through the gaping windows, smooth and sleek like the silken coat of a lioness.

Neither wanted to speak and break the spell that had fallen over them, so pure in its magic that even the air glittered as dust motes passed through light beams with the timing of dancers.

"Dress for the sun," was all Castle could mutter quietly, gracefully slipping his hand beneath Kate's head and slipping off the bed, transferring her skull to a pillow. Her eyes never left him, though she did not even smile – her expression did not change.

Castle went to cook a breakfast of well-seasoned scrambled eggs while his queen showered and dressed in cropped jeans stopping above her knees and a faded flannel shirt enriched with blues, indigos, violets and reds, weaved through with white streaking across the softly tumbling cotton. Her hair was still wet when she emerged and Castle's eyes darted towards the red door, its silver embellishment borrowing a shard of sun. Kate noticed the movement and smiled, reaching out to him. He kissed the top of her scalp, the heady sent of cherries stealing him away to some kind of awe-filled dream world, while her arms slithered around his waist. They held each other in his kitchen for quite some time, dancing slowly and melodically in time to some unsung ballad that could be written only from the pulsing of two hearts coming together in that star-like moment. In the grand scheme of things, stars exploded and islands erupted from oceans and comets flew across the sky, but Rick could not bear to peel his eyes from Kate's unrelenting stare; they stood drinking each other in, the filling feeling of love causing them both to shiver.

They were forced to part when Castle feared that their breakfast might burn and he had to keep stirring, popping some bagels into the toaster as he went. It turned out all right and they enjoyed it with some freshly squeezed orange juice. After clearing their plates, Rick leaned down to kiss Kate gently on the lips, a soft temptation and cruel promise, for when Kate reached up, eager to tangle her fingers in his hair, and her chest started to heave, he broke away and slid over past his bookshelves to cover his blue boxer shorts with khaki cut-offs and a grey V-neck T-Shirt. He also grabbed a tote bag, trying to be discreet in his methods so Kate wouldn't immediately guess what was going on as she so often did.

Together they left the apartment, hand in hand, and walked along the sidewalks heading toward Central Park, their flip-flops clapping in eager unison. They stopped to watch the Hudson flowing past and glowing white in the heat of the day, forcing them to squint even wearing their sunglasses – Kate sporting nondescript aviator frames and Rick with more sporting style – before grabbing a cab north from Tribeca all the way up to Central Park West, never breaking their handhold for even one second.

Strawberry Fields was a quiet part of the woods of Central Park, but the traffic sounds still echoed from tree to tree. Kate and Rick were used to tuning out that noise, and did so now, enjoying blissful peace as they joined the path that looped The Lake and continued to walk, simply enjoying moments in each other's company. After crossing through Bank Rock Bay, they entered the deepest woods of The Ramble, where all they knew were leaves and birds and sun and each other's shining eyes.

The pair reached a small clearing that was almost perfectly circular. The grass was so long it tickled their interlocked hands as they waded through it, and it was dusted with daisies and dandelions.

Castle confided that this was one of his favourite places. Almost no one could find it, because they stuck to the wider trails, and this meadow was a quarter mile out from one of the more minor paths. He himself had discovered it as a child, tempting fate by escaping his mother's keen gaze, only to be located hours later by park rangers when he emerged two hours later right back on one of the main roads. He knew this part of the park better than he knew how to navigate his own apartment building; he did not, however, know its paths quite as closely as he knew those of the woman beside him, who, in the heat, removed her shirt and stood in a simple white vest, her shoulder blades clearly defined through the fabric, her long, graceful neck exposed beneath her messy bun, and the dent of her lowest rib barely visible as her figure curved inward towards her waist.

Rick invited Kate to sit with him beneath his favourite tree, an oak he believed to be the oldest and widest in central park, and together they leaned against the trunk and each other and at their modest picnic of deli counter sandwiches and bottles of water.

Once finished, they lay back in the soft grass, nature's very own pillow, and gazed upward. When Kate unfocused her eyes she could watch as the green of the leaves grew fuzzy, like in movies when car taillights faded to sequin-like red blurs. Twinkles of green and blue dazzled her vision and it felt like she was in some kind of magical garden, not her own back yard. They analysed the clouds as they passed and named their bizarre shapes, laughing and smiling all day, losing hours to each other in unmitigated happiness.

They could have sat like that, in that jewel-like moment, that pocket of perfection, away from the ailments and complexities of life, forever, completely content with their surroundings, their being and, most of all, their partners.

But when the sun tilted low enough in the sky, announcing that it was almost time for dinner, and its whiteness became a warm, orange glow, they had to stand and start making their way south, still dreaming, and still smiling and laughing. Castle knew the way, of course, and Kate had complete faith in him. She never questioned where they were, or which way they were going, or whether he remembered the paths, because she trusted him so completely and she knew he would never guide her falsely. He would never mislead her or take her somewhere if he didn't believe he could keep her safe. She was safe. He made her safe.

They walked along paths so old they were now grass tracks, thriving with spring wildflowers of vivid colours in rainbow hues, wonderful scents filling their air where the taint of traffic could not touch, and where the track lay so undisturbed they could have been ambling through history itself, back to before – before all the skyscrapers, before all the cars, before all the grey and dreary. Here there was light and brightness. The first bees hummed and a dragonfly zipped past; even a butterfly flickered through the air, making the most of its warmth, its early summer. The only sounds were the birds' whistles and calls and melodies, and the swishing of the grass and the leaves in the lightest breeze, and the beating of two hearts travelling through the enchantment.

They emerged on Bow Bridge at last and Kate smiled, stopping to rest her forearms on the railing and gaze across the water. It was a sad smile, because her day with Rick was almost at a close. But it was also a hopeful smile. Summer was coming, bringing more new days and more nature and more time with Castle. He highlighted everything in her sight – he brought all those wonderful things to her attention: The trees and the birds and the insects. Without him, she walked past them blindly. She needed him to be her sight, for he had the clarity of a perfect diamond inside him. She knew it.

And so their spring ended. With a hopeful smile.