Paul Thompson sat in the interrogation room, looking shifty.

Beckett entered at sat down across from him.

"Hey can we make this quick? I'm supposed to be filming right now."

Beckett looked at him like she couldn't care less.

"Mr. Thompson, we know that you have Hepatitis C and so did Alana. We did an analysis on your particularl strain and matched it to Alana's blood results."

Paul swallowed.

"So", Beckett continued. "We know that no one wants to sleep with someone who is infected with a virus. So did you just not tell her you have it?"

Paul shut his eyes. "We never slept together."

Beckett looked confused. "Excuse me?"

Paul sighed. "Look, I didn't know I'd infected Alana until she started turning down every single meal and complaining of constant itching. Classic signs of Hep C. I know it sounds unlikely but just here me out ok?"

Beckett waited for him to continue.

"Alana's ex, Michael came to the studio one day to see her, starts pleading like a fool with her to give him another chance, but she told him that she'd moved on and that we were together now. As you can imagine, that went over real well. He found out where I was and ended up knocking a couple of my teeth out. I didn't even think about the fact that I had open sores in my mouth the next time Alana and I kissed. It was her that initiated it, she was just so relieved that crazy ex of hers hadn't killed me. She really was sweet."

Beckett wasn't buying his story. "You're telling me you infected Alana by just kissing her?"

Paul shook his head sadly. "I can't believe I didn't think about the cuts. Poor Lana."

...

"I can't believe it. How is that even possible? It's like some sort of freak accident, right?"

Castle and Beckett were sitting in the living room of a very confused Melanie Vestig. They had promised her they would tell her exactly how her sister had contracted the disease as soon as they found out.

Beckett didn't want to stress the victim's sister too much, but there were some things she needed to get straight.

"Miss Vestig, how long were Alana and Paul seeing each other? Only he mentioned to us they hadn't actually been... intimate yet." She didn't think the woman needed to hear about her sister's sex life.

"No, no Alana was not seeing that guy. She always said he was a creep."

"Is it possible that this was one thing Alana didn't share with you?" Beckett asked gently.

"No." Melanie was defiant. "My sister had higher standards than that. MUCH higher standards."

Castle and Beckett looked at each other, now even more confused.

...

Back at the precinct, Beckett, Castle, Ryan and Esposito were all sitting in silence, each mulling over their own theories in their minds.

Castle squinted at the board, his lips pursed, and then turned to Beckett.

"Let's just try something...come at me like you're going to kiss me".

Beckett blinked at him "What?" She said it rather loudly, and straight away Ryan echoed the short question, looking up at Castle with a bemused expression.

At once, Beckett's heart began beating at a rapid pace, but Castle looked at her dully

"I'm not actually going to kiss you, just running theory".

Beckett's face showed disappointment "Oh... alright then".

She cleared her throat and unconsciously licked her lips before very slowly rising from her seated position on the corner of her desk and tiptoeing, like a cat, toward Castle.

Castle had been truthful when he told Beckett he wasn't going to kiss her, but seeing the way her eyes were burning into his, in anticipation of whatever he was planning to do, all of Castle's intentions went out the window. Beckett was just beginning to wonder when he was going to stop her, when suddenly his lips were on hers.

Beckett's entire body froze; her brain and heart were no longer connected, and yet both had stopped. She forgot who and where she was and she drew in his scent as he deepened the kiss for the briefest of moments, before Beckett snapped back to reality.

She pulled away quickly, regrettably and tried to look angry at Castle. "I thought you said you weren't going to kiss me",

Ryan and Esposito were staring at the two of them, wide-eyed and open mouthed.

Castle, who was red in the face, said one word in reply "Exactly".

Now Beckett was confused. Castle took a rather shaky breath before continuing.

"Alana was in a relationship with Michael, when he becomes envious of her success as an actress, they break up. A few days later he comes back to her, begging her to take him back, saying he was sorry and that he'd been petty. But she's famous now, she doesn't need a drop-kick like him. So she lies to him stating that she is in love with her acting partner, Paul. Michael doesn't exactly take rejection easy. So he goes to see Paul and punches Mr. acting partner in the face, causing a tooth to become lodged in his gum, and Paul starts bleeding from the cuts. Now, Paul has always had a thing for Alana so when he thinks what Michael is saying is true, he makes his affections known to her, but she of course lets him down... and not so gently either, telling him she only said that so Michael would leave her alone. This doesn't go over so well with Paul. Next time they're running lines, he kisses her, but he had to keep it going long enough for the disease to transmit. And I think I've just proven that it is in fact possible to subdue someone who is totally unwilling, for just long enough."

A wistful look dressed Castle's face. "She just thought he was obsessed with her, she never knew he was trying to kill her."

Esposito brought him out of his daze. "Man, that theory is completely nuts. IF it's even remotely possible to get Hep C by kissing..." Castle interrupted. "Six cases in New York City in the last year of Hep C oral transmission". The three cops looked at him strangely. "Research for one of my new characters - that's a spoiler, no leaking". He put a finger to his lips.

Ryan spoke up. "There's another flaw in your logic." Castle looked indignant. "What's that?" Ryan looked at Beckett and then back at Castle. "This Paul guy was so far out of Alana's league it wasn't funny. There was no way Alana would want those greasy lips anywhere near her where it wasn't necessary. She would've pushed him off at the first inkling that he was getting anywhere close to being out of character." Castle's eyebrows furrowed. "What about me and Beckett just then, she wasn't up for any kind of "mouth contact" and she went with it... for a while." He leaned in discretely to Ryan and whispered. "And there was definite tongue action".

"CASTLE!" Beckett had heard him, and was now a bright shade of pink.

Esposito peered up at Beckett. "Unless Beckett actually enjoyed being kissed by Castle?"

Castle's eyes bulged open and his head flung in Beckett's direction, tensely waiting for her reply. Ryan and Esposito were staring up at them both, waiting on tenter hooks.

Beckett longed to tell the truth, to not have to lie anymore, but she just wasn't as brave a woman as she was a cop.

She put on a straight face. "Of course not."

Castle looked at her, crestfallen. She had forced a smile onto her face, but there was nothing but sadness in her eyes.

A young cop approached Esposito and gave him a picture. He thanked him and then looked very intently at it. He turned to the rest of the team.

"Guys." He said to get their attention. "CSU just came back with a very interesting picture of Michael Zivanovic from around the time of the murder. Guess where security footage places him."

He spinned the picture around so everyone could see. Castle was the first to speak. "That's Alana Vestig's apartment building."

Esposito nodded with a satisfied expression.