"So, it wasn't a dream!" Richard Castle says early on during Monday's Season 5 premiere of ABC's Castle.Nathan Fillion ) is, of course, expressing his excitement about having finally hooked up with his muse, NYPD Detective Kate Beckett (Stana Katic) after four long seasons of will-they-won't-they drama. Had it all been a dream, it would have been a nightmare scenario for fans — and for the show's creator, Andrew W. Marlowe."We had kept them apart as much as we could while still being credible," Marlowe tells TVGuide.com. "Keeping them apart would have felt artificial and would have damaged the show."But before anyone even utters the words "Moonlighting curse," Marlowe wants to make one thing clear: He's confident the hookup and its implications will change very little about the way Castle and Beckett interact. "These two people are strong-willed individuals," he says. "They are not going to change who they are because they're in a relationship. All the stuff that got on each other's nerves before will certainly get on their nerves now."Tahmoh Penikett), the man who shot Beckett in the Season 3 finale, vowed to "put Kate Beckett in the ground for good." And he wasn't lying. "Beckett is still under threat," Marlowe says. "When [they] wake up the next morning ... in that blissful bubble that they may be in, life has a way of coming in and bursting that bubble. Real life intrudes really quickly, and that is part of Beckett's journey."Jack Coleman), who Marlowe says has some "compelling information" about Beckett's mother's murder. But now that she's closer to the truth than ever, Beckett's actions may surprise you. "We follow a trail and discover that [Bracken] is somebody that has some insight into what's going on," Marlowe says. "It's going to spin our characters in a different emotional direction. Once Beckett has that knowledge, what's she going to do with it and who is she going to become?"With the prospect of finally putting her mother's murder behind her, will Beckett finally be fully able to commit to Castle? And can Castle turn away from his millionaire playboy lifestyle? These are the questions that Marlowe promises will keep the tension between Castle and Beckett as thick as ever.