As Castle tried to button his jeans and failed, he realized that he finally had to admit that he had gained a few lbs over the summer. Between eating out every night on book tours and the amount of alcohol he was consuming while worried about Beckett, he noticed that he was getting a little soft around the middle.

Considering that he was hoping to have a chance with a woman who looked like a supermodel, it made him start to worry. So when he knocked on the door to Beckett's apartment and she admitted that she had been spending her Friday evening doing yoga, his little weight problem seemed like the most important topic at the moment.

"Yoga, Castle…I was doing yoga." Beckett's regarded him, a twinkle in her eye establishing that she understood what he thought her breathlessness meant. "What do you need?"

"I need to get in shape," Castle said, the words falling out of his mouth before getting the chance to stop them.

"So…you want to do yoga?" Beckett's asked; a smirk on her face.

Castle recovered, realizing that since he already opened this can of worms, he might as well finish it.

"I was thinking more along the lines of running. I know you said that you were training for that half-marathon, trying to get your heart back in shape. I was wondering if I could join you?"

Beckett's eyes moved from his legs, then chest, then face, seeming to scrutinize every inch of him.

"6am tomorrow morning, at the path by the swings…go get fitted for running shoes if you haven't yet." Beckett wiped her face with her towel.

"Meet you there," Castle nodded his head as he began to move out of her doorway.

"Castle," Beckett said before he had gotten more than a few feet down the hall.

He turned around, acknowledging her.

"You look pretty good to me."

A smile broke across his face as he waved goodbye.

"See you tomorrow."

…

The water poured down from the sky, soaking Beckett's skin. Rain or shine, she would always make it to her Saturday morning run. Her heart wasn't going to get stronger if she didn't exercise it. She glanced down at her phone, expecting to receive a text from Castle, saying that he was going to sit this morning out. Instead she heard the sound of pellets coming down on a raincoat.

She turned around and laid eyes on him, dressed from head to toe in new gear. His red nylon shirt seemed to cause the blue in his eyes to sparkle a little more. She tried to stop the rush of desire that fell over her. Castle looked hot.

"Hey Castle, didn't know if you were going to make it." She turned her Garmin watch on, hoping it would still catch a satellite in the rain.

"Wouldn't miss it for the world…so, where are going?" He reached down and turned his own Garmin on. Beckett grinned as she realized that he would buy a GPS watch for the first time he ever went running.

"We will run through those trees and around the park. It will be a short run today, about three miles. I'll go at a bit of a slower pace since you are new to running. But try to keep up as best as you can. " Beckett pointed to the rain soaked path, surrounded by large, blowing trees.

"Oh, I can keep up with you," Castle winked at her.

Beckett rolled her eyes and started running, "Don't finish too early, Castle."

…

Five months later, Castle was running past mile marker twelve. He couldn't believe how far he had come. Today was the day that he was finishing his first half-marathon, 20 lbs lighter and better than he had felt in a decade.

Unfortunately, he didn't have his partner beside him to run. Beckett had sprained her ankle a week ago, taking her out of the race. She also got called into work today, but said she would do her best to cheer him on. It had been fun training with her. That first day of running, Castle had only made it about a mile and a half before keeling over, out of breath. Beckett had been surprisingly patient with him, walking the last bit so that he could finish alongside her.

Over the next few months, they would meet up three or four times a week to train. Each day, Castle found himself getting stronger and faster. After a while, he was running the same pace and distance as Beckett. But the best times were when they would train in the evening. Sometimes they would catch dinner after their run and talk for hours.

Castle was devastated when Beckett sprained her ankle and found out she wouldn't be able to race with him. But she encouraged him to do it anyway. Castle knew that while Beckett had helped him get to this point, he had done the hard work and he was proud of himself for it.

As Castle saw the finish line, he picked up the pace. Beckett had told him that most people sprinted to the finish. Castle was prepared to do that. What he saw at the finish line were the three women that he loved more than anything. His daughter was holding a sign that said, "Run like you stole something" and his mother was clapping her hands. But next to them was a beautiful woman, a brace around her ankle, holding two coffees in her hands. As he ran past the finish line, he heard, "Go Castle, dad, and Richard." Three different names describing the relationships he had with the three women.

Alexis and Martha pulled him into a sweaty hug, "You did it!"

Martha looked over at Beckett as she hobbled over, "Alexis and I will pull the car around. We will come pick you up so neither of you have to walk very far."

"Congratulations, Castle." Kate said, handing him the coffee. "It's cold, because I didn't think you would want a hot beverage after that run."

"Thanks, Beckett. I'm just sad that you couldn't do it with me." Castle brought the cup to his mouth, the delightful taste quenching his thirst.

Beckett put her hand on Castle's chest. "Castle, training isn't the only thing that I've been working on these past five months."

Castle wondered what else she could mean. As far as he knew, training and working is all that Beckett has had time for. "What else have you been working on?"

Beckett's face was so close to Castle's that he felt as if they were breathing the same air. "Castle, I love you too."

Her lips took hold of his and all Castle could think was, "13.1 miles…worth it."