A/N: First Castle fanfic, please review. Especially if you have a critique, it's honestly better than praise. Set during/ a little after "Den of Thieves."

Kate Beckett stepped out of the break room, hearing the familiar sound of her heels clicking against the worn wooden flooring, to see Castle sitting at her desk, guzzling down both Styrofoam cups of coffee he had carried into the precinct that morning. "I should have called you to let you know I was getting coffee with Demming," she apologized, sliding into the rolling chair beside him.

"Oh, it's fine," he said, waving it off as he chugged the last few sips of the second cup. "I got both of these for me. Really tired this morning. And thirsty." Maybe it was because she'd known him for a year, maybe it was her experience from interrogating suspects, maybe it was because she read so much into his books, but she could tell that there was something he wasn't telling her.

"Castle?" she said, turning to him.

"Hm?" he replied. A thin line of coffee had appeared over his upper lip due to his hasty drinking. He wiped it away with a corner of his sleeve.

"Do you have a problem with Demming?" she asked bluntly. Ever since Esposito's former partner had showed up to help him with their case Castle had seemed distant, bitter. She recalled some of the things he'd speculated when they all thought Demming was their suspect.

"Demming?" he said. He tried to sound nonchalant, but it was obvious to her that he was faking it. Why, she couldn't be sure. "No, he's great. The way he just sweeps in here all… great. No problem at all." As he squinted into his coffee cup for extra dregs of coffee (and winced when a lingering drop attacked his eye), he muttered, "He's a murderer."

"You still think he has something to do with Finch's murder?" she asked, surprised. She assumed it was another of his crazy theories. She had her money on an identical twin story.

"He's a murderer of love," he mumbled back, grabbing his jacket off the chair and standing up.

"Love?" she replied, shocked as she, too, rose to her feet.

"Yeah," he said, obviously uncomfortable. "Uh… brotherly love! Yeah, the Ryan-Esposito thing, he ruined that. They're not even talking anymore."

"That's not true," she said, hand on her hip, for the first time in her life actually curious to know what was going on through Castle's head.

"I have to go," he said, putting his coat on backwards. "Alexis is sick."

"She was in here this morning," Beckett reminded him, slipping into her cop persona as she picked through Castle's lies.

"I have a book signing," he rambled. "I mean… laser tag date. Is that a door?" He hurried out of the precinct, still struggling with his jacket, leaving her standing there rolling her eyes, as usual a little bit baffled and a little bit scared about what Castle had said.