A Man's House Is His Castle

Summary: When Castle is suddenly taken ill at a book signing in New Jersey, his case attracts the attention of Princeton Plainsboro's best diagnostician.

A/N: I was a little surprised when I saw that nobody has done a House/Castle crossover before, as they're two of my absolute favourite TV shows and I'd love to see how they could be made to work together. Since nobody has written one yet I decided to start working on one myself. I've never written a House fic before now as I've always felt my medical knowledge wouldn't be sufficient to make it authentic, but since I've recently started doing historical research for one of my other stories I've decided there's no reason I shouldn't do medical research for this one. So, here it is and I hope you enjoy it!

Disclaimer: I own neither House nor Castle.

Chapter One: An Unexpected Turn Of Events

With a final flourish of his pen and flashing a charming smile, Richard Castle handed back the freshly signed copy of Frozen Heat to the fan in front of him. She took it out of his hands with a huge grin, and semi-squealed "Thank you," before moving away to allow the next in the line to come forward. Inwardly, Castle sighed to himself, wishing the next thirty or so minutes would pass quicker so the signing event could be over and he could go home. It wasn't that he didn't appreciate his fans – on the contrary, he was well aware that they were the reason for his success and was immensely grateful for their support - but this promotional book tour felt like it had gone on for too long now. He'd spent last week in North Carolina visiting several bookstores to promote his latest Nikki Heat novel, and then travelled north through Virginia and Maryland for a few days before finally reaching New Jersey, where this would be his last signing session before a couple of brief interviews in the morning and then travelling home to New York tomorrow afternoon.

Tomorrow afternoon was something Castle was very much looking forward to. It had been over three weeks since he'd last seen his daughter or his mother, and although he'd gone without seeing them for longer before, coupled with him not having seen Beckett or his friends at the twelfth either was making him start to feel a little isolated. True, Gina and her assistants were travelling with him, but he'd found that ex-wives he'd split up with twice and near strangers didn't make the best company. What he really wanted was to see Alexis again. And, perhaps just as much, he wanted to see Beckett.

The thought of her was how he managed to keep putting on the smiles for the last few people in the queue, despite the fact that he was feeling exhausted. Really, he couldn't remember promotional tours ever being this tiring before. They'd been pretty demanding, yes, but never before had they left him feeling this completely drained. He wondered if perhaps it was his age showing.

As the queue dwindled and only about ten or so people remained, Castle reached for the glass of water on the table by his hand and downed the last few millilitres from it. He'd had a steady supply of water throughout the day, but by now the bottles of mineral water Gina had ordered for the event had pretty much been emptied and Castle was still feeling somewhat thirsty. Only a few more minutes to go now, then he could get some water from the tap before heading straight back to his hotel room and treating himself to a Scotch.

"Who should I make it out to?" he asked the fan in front of him, a girl of about eighteen with short brown hair and blue eyes, who looked absolutely delighted to be meeting him.

"You could make it out to me," she responded a little shyly, "It's Kate."

Castle felt a slight pang as he was reminded even further of the woman he was missing seeing, but it wasn't wholly unpleasant. "Kate, huh?" he said, smiling as he opened the book to sign the first page, "That's a pretty name."

Kate blushed. "Thanks," she said self-consciously, "That's her name, isn't it? The inspiration for Nikki Heat?"

Castle looked up at her. "Yes it is. The wonderful Kate Beckett," he said, having just finished writing the 'To Kate' part, and then he paused for a moment with the pen hovering over the paper. A slight headache was beginning to bother him now, probably a result of tiredness and dehydration, but he still wasn't going to rush through these last few signings. In particular, he'd picked up something in Kate's accent that intrigued him. "Where are you from, Kate?" he asked her, "Not New Jersey?"

She shook her head, looking both disbelieving and flattered that he was actually showing an interest. "No, I'm from England. I'm here to study at the university."

Seeing how nervous she was, he continued to smile warmly at her. "What are you what are you majoring in?" he asked, setting his pen to the paper to sign his name.

"Astrophysics," she answered simply.

He paused again and looked up. That was actually pretty cool, and not an answer he'd been expecting. "Space and stuff? Sounds cool," he said, and was about to make a further comment when he suddenly felt a wave of nausea wash over him. He felt a brief but very strong urge to be sick, and as it passed he gulped down a breath of air to try to clear his head.

Seemingly oblivious to his discomfort, Kate continued talking, "I know that probably sounds like I should be really into science-fiction and Douglas Adams and stuff, but I really love crime novels too. It's great reading about all the twists and turns in a murder investigation and trying to work out how it all fits together. You're definitely my favorite crime writer. You have this way of really getting inside the minds of the characters, making you feel what they feel, explaining their thought processes, you know?"

She was gushing now, but Castle was still preoccupied with trying to overcome the strange sensation he'd just felt to really pay much attention. What had brought that on? Was it really just exhaustion, or was he coming down with something? Well, whatever it was, he'd just be very grateful for a drink and a lie down once this was over. Drawing another deep breath, he forced himself to focus on just getting the signing session done so he could get back to his hotel. As he lowered the pen again to try and finish his signature, he was surprised to see that his hand was shaking. Forcing himself to continue anyway, he scrawled down a messy autograph and shut the book to hand it back to her.

"There you are, Kate," he said, reverting back to autopilot and just repeating his standard sayings for signing sessions. The smile he was giving her was stretched somewhat thinly now. "Thank you very much, I hope you…" he began to say, but trailed off again as he felt another rush of light-headedness.

He really didn't feel well at all, and shut his eyes as Kate took the book off him. He wasn't really paying attention enough to register her reaction, but he vaguely heard Gina saying somewhere behind him, "Rick, are you alright?"

The truthful answer to that was 'no'. He was starting to feel incredibly hot, and he could tell his face was flushed and beads of sweat were beginning to form on his brow. Yep, he must definitely have come down with something. Just when he thought he could get back to working with Beckett and the others at the precinct tomorrow…

But what had brought this on so suddenly? He started to try and ask Gina for a glass of water, but breathing had suddenly become difficult and the words wouldn't come out. As he looked round to see where his publicist was it was with a sense of panic that he realised his vision had begun to blur. This must be even worse that he'd realised.

"Gina…" he managed to choke out, but when the people around him answered their responses sounded somewhat muted. Oh hell, what was wrong with him?

Thoughts of Alexis and Martha and Kate flooded into his head as he wondered what he was going to tell them and if he would get to see them tomorrow after all. He felt sick. Really sick. And it scared him even further that he didn't know what was happening to him.

Around him everything had blurred into a haze of panicked voices and people talking over each other in urgent tones, and as his vision began to darken the last thing he saw was Gina standing over him and looking down at him with a worried expression before everything went black.

A/N: Yes, there's a rather shameless self-insert this chapter, because it's based on a real-life experience I had and I figured that since I only would have written a character called Kate anyway, why the hell not? I've avoided writing the part with House this time, as I'm still debating with myself what season of House I'm going to set this during. I know it would mean taking liberties with the timelines, but I think I intend to set it during season five or six because it will give me chance to use my favourite characters. At any rate, I still need to get some research done before I get round to writing that part. And I really, really need to stop publishing new stories because I can't possibly keep up with all of them. But also, I can't keep ideas in my head once they pop up, I have to write them down! So, if you liked this, thank you in advance for your patience with an update, and reviews would be much appreciated.