Happy Castle 100th, everyone! Sadly, I'll have to wait until the episode is available on iTunes here in the UK but hopefully that won't take too long this week.

Thank you so much to everyone who's following this story. Here's the penultimate chapter.

Disclaimer: Castle is most definitely not mine but many congratulations to all the cast, crew, creators, writers and everyone else involved in bringing us 100 amazing episodes. Here's to the next 100!

Chapter 8

"After four years working side by side you finally changed the status of your relationship, how did the publicity that must have prompted impact on your life? You were and, to a certain extent, still are a very private person; it must have been a difficult adjustment to make."

We did actually manage to keep our relationship to ourselves for a while although evidently not quite as well as we thought. Martha found out that very first morning. She'd arrived home unexpectedly with Alexis and, although we didn't know it at the time, had spotted me hiding in the closet! Please don't ask anymore about that! Castle also told his daughter just before she headed off to Columbia. I had been a little concerned about Alexis's reaction; she and her dad had always been so close and I knew that she felt I'd hurt him by my actions rather too many times but I really wanted her to be happy about our relationship. As it happened, I had no cause for concern. Once she saw that I was really in for the long haul, she was happy for us and since Castle and I have been together I've always thought of her as my own daughter.

I told my dad early on which was no problem because he'd always liked Rick and appreciated just how good he was for me. We were, of course, both children with only one parent and I would like to think that Martha and my dad managed to fill a small part of the gap left in each of our lives.

As for other people, well at the precinct, Kevin Ryan was the first person to find out, or at least that's what we thought until we discovered that Victoria Gates had actually known from day one. Javier Esposito and Lanie Parrish found out soon afterwards during a terrible case when Castle had been totally set-up to take the blame for a murder by a killer known as 3XK, or The Triple Killer. It had been our intention to keep our relationship from Captain Gates for as long as possible because NYPD regulations prohibit relationships between co-workers. However when she finally let on that she had known all along, she said that she had always made it perfectly clear that Castle was not a member of NYPD and therefore was classed as a civilian, not a co-worker. Basically she let us off the hook and for that we are eternally grateful.

We couldn't hope to keep our relationship out of the press for ever and eventually a photographer caught us making out in public and the proverbial hit the fan. We managed to keep the press off my back at work after several threatening letters from Paula Haas, Castle's publicist and also from his buddy, the mayor but the price was my attendance at all publicity events from book launches to film premieres. In those early days we also agreed to do a good number of press, radio and television interviews and by playing ball, giving them a certain amount of what they were after, it helped us in the long run. Nowadays, well, damn it, the parties are fun.

I don't think Paula liked me very much to start with. She had spent years building Castle's playboy, bachelor around town image, an image that he'd been very happy to live up to. That was until I came on the scene and he realised that he wanted more than just my friendship. Then he began to rebel against Paula's well-laid plans. As it turned out, she needn't have worried. It appeared that the public are romantics at heart and the story of the playboy author who fell in love with his muse (God, how I used to hate that word!) came to sell far more books than his previous image had ever managed.

"I believe that one thing neither of you have ever disclosed to the press was how he finally proposed. Are you willing to do so now?"

Kate had to laugh at that question. She knew that her son was very well aware of the circumstances and that the story lay in the fact that there wasn't really a story to tell. Unusually for Richard Castle, it had actually been a very low-key event.

Oh, I think the world would be very surprised how that happened. I had come to believe that it was unlikely that Castle would ever be prepared to marry again. He had two failed marriages under his belt and I knew that there was a large part of him that was petrified of a third failure. However, I have been known to be stubborn on occasion; I had told him very soon after we met that I was a 'one and done' type of girl and once we were finally together, it had taken me no time at all to be certain that Richard Castle was my 'one and done'. I was ready and I wanted the whole nine yards, marriage, home, family. I just had to figure out how to get Castle on the same path.

In the end, it was actually a comment from his first wife that gave me the clue I needed to solve the problem. I think Meredith was probably trying to put a spanner in the works of our fledgling relationship when she told me her thoughts as to why their marriage had failed. She said that although he knew everything about her, the things that she knew about him would barely fill a pamphlet; and the more I thought about that, the more I realised that to a certain extent that was true of us as well. He had spent four years learning every tiny detail of what made Kate Beckett tick and yet, although I was sure that I knew a great deal more about him than Meredith probably ever did – he had told me a lot over the years – he had a wall of his very own and before I could ever hope for the happy-ever-after I was looking for, it was my turn to try my hand at demolition. I only hoped it wouldn't take me another four years!

As it happened, it barely took me four months! As I say, I can be very stubborn, rarely take no for an answer and, for God's sake, I'm a detective and expert interrogator. I'm not prepared to go into the details because that is his story not mine and as far as I'm concerned it will remain between the two of us but I was right and once that wall fell, his proposal followed very quickly.

Years earlier, when Kevin Ryan was seeking advice on how he should propose to Jenny, Castle had come up with all sorts of spectacular ideas but I had said that what a girl really wants is something intimate. As always, he was listening, taking note and filing the information away because we'd just finished up a really tough case and were having our first evening together in a couple of weeks. We were at my place and had ordered a pizza. Once we'd eaten and just as I thought we were settling down to watch The Princess Bride for the thousandth time, he suddenly dashed to the bedroom. I could hear him frantically searching through drawers, muttering to himself, rather loudly I might add and then before I knew it, he was back, kneeling in front of me and taking hold of my hands. He looked me straight in the eye and just asked, "Kate Beckett, will you marry me?" Obviously I said yes. That was it; nothing spectacular, nothing ostentatious, simply intimate.

"You married shortly after in the Hamptons, I believe?"

That's right. It hardly seemed worth having a long engagement, we'd wasted enough time already; so three months later we married on the beach in the Hamptons. It was a wedding much like the proposal, intimate but oh so meaningful, in front of a handful of our closest friends and relatives. Then we spent an amazing two weeks in Italy on our honeymoon and in no time at all we were back at work.

"Castle carried on working with you at the precinct after your marriage. How long did that continue?"

We worked together until our son was born less than a year later. Just as we saw no point in a long engagement, there was also no reason to delay starting the family we both wanted; in fact as neither of us was getting any younger, time was of the essence. After our son, Ryan James, was born, once my maternity leave was over, I headed back to the 12th while Castle stayed at home to look after the baby. Maybe it was a strange role-reversal but when it came down to it, he had more experience than I did as far as bringing up a child was concerned.

"Was it an easy decision for you to return to work?"

No, it wasn't. We talked about it from the moment I discovered I was pregnant and the decision was only really finalised when my leave was due to end. My job had been my life for a very long time. It had been the dominant force until Castle appeared on the scene and my priorities changed somewhat. However, I still loved my job and was unsure who I could be without it. On the other hand, life as a cop has its risks. I'd lost my mother to a violent death; in my line of work, the chances of that happening to me, the chances of depriving our son of his mother were so much greater. In the end it was Castle who finally convinced me that I could just as easily be killed in a car accident and that the precautions we always took were sufficient to keep me as safe as was feasibly possible.

"It can't have been easy continuing to work as a cop during pregnancy. You must have found that a tricky balancing act, doing your job and at the same time keeping yourself and your unborn child safe."

RJ was suddenly aware of a tensing of his mother's position on the couch. She had been so relaxed throughout their interview and yet now it was blatantly obvious something had changed but he had absolutely no idea what it could be. Kate had never been very good at hiding her emotions from those who knew her best and it was clear to him that, at the moment, a serious debate was going on in her head. It did not go on for too long, though, as she slowly raised her head, looked him directly in the eye, took a deep breath and spoke in a quiet, controlled voice,

"Go get your sister, there's something you should both know about."

He was about to speak but one glance at Kate's expression told him just to do as she asked and save the questions until later. He went up the stairs to find Beth.

Ooohh! What's going on? Final chapter will be up tomorrow, I promise.