Dappled afternoon sunlight, scattered by the clouds, played across the landscape Central Park, creating zigzag patterns on the ground through the blades of grass. A light breeze toyed with the leaves in the trees. Children on the carousel laughed. Voices echoed across the grounds, quiet as they were swallowed up by the vast park.

A murderer sprinted across the grass, swiveling his neck around behind him to see Detective Beckett and Castle coming after him.

"Freeze! Police!" shouted Beckett, but to no avail, their suspect only ran faster. She regretted not bringing Ryan and Esposito along, but she hadn't counted on this man being their killer. She hadn't counted on Castle figuring it out halfway through their conversation with him, and she hadn't counted on him announcing his realization loud enough for the killer to hear.

It was dawning on her that she really should have been more prepared going into this.

The man ahead of them ran into the carousel, which was still spinning around. A few mothers, after noticing the chase going down, had plucked their children off the fake horses with the ride still in motion, the way one might pick up his suitcase off the baggage claim conveyor belt. Instead of running around the carousel, the man just jumped up on to it, grabbing the pole of a vacant pony when he lost his balance.

Kate reached the carousel soon after and swung up on to it, Castle clambering up behind her. She'd expected their man to hop down as soon as he reached the other side, but evidently the drop from such a high velocity had frightened him, because he'd gone around again and was just to their left, hanging onto his horse.

She lunged towards him, her hand just missing the fabric of his shirt as he tore away and started running clockwise around the middle of the carousel. She ran after him, the floor sliding backwards beneath her like she was on some kind of circular treadmill.

She caught him as he tried to hurdle over a horse, pulling him down and forcing him up against the side of the plastic animal before handcuffing him. "Henry Bayer, you're under arrest for the murder of Monica Newton. You have the right to remain silent. Anything you say or do can and will be held against you in the court of law."

While she read Bayer his Miranda rights, Castle leaned against one of the horses and glanced at its fake mane thoughtfully. He remembered coming here with Alexis when she was younger, lifting her up onto the saddle and keeping up with the moving carousel so that he could keep an eye at her at all times- well, he'd only done that once, after which Meredith had teased him relentlessly for it and he'd decided to stick the ride out in one spot.

He'd been thinking about the "good old days" a lot recently, Castle realized now. For the past week he'd been reminiscing and getting nostalgic whenever it came to Alexis. He'd even welled up a little last night when he'd noticed Monkey Bunky hitching a ride at the top of her laundry basket. It had to be the college thing, the fact that she was ready to leave him and head off to Stanford. She might be ready, but he knew he wasn't. He wasn't ready for her to grow up, to be too old to ride the carousel.

It was selfish, it was silly, and it was irrelevant, so he shook these matters from his head (or tried to, at least) and went to meet his partner with the suspect.

"Nice catch," said Castle once they were back at the precinct, heading to Beckett's desk.

"Thanks," she said, sinking into her chair. "Next time just elbow me or something if you figure out that we're talking to the killer, 'kay?"

"Sure," he said with a laugh, nodding.

"I hate it when they run," she sighed, mainly to herself, as she started filling out a post-arrest report.

"Could've been worse," Castle pointed out. "He could have galloped. Or trotted. Or cantered." She shook her head, laughing more at him than at his joke, and returned to her paperwork. He smiled, realizing that just because Alexis was growing up didn't mean he had to. There would still be a kid in the Castle household, just like there always had been.