Nathan Fillion

It’s precisely the kind of chilling twist Richard Castle might concoct. On a Hollywood soundstage in early February, the mystery novel-penning protagonist of ABC’s Castle, played by Nathan Fillion, is shadowing his muse, no-nonsense NYPD detective Kate Beckett (Stana Katic), as she tracks a person of interest to a storage freezer in Manhattan. Too bad the guy, who’s already taken a bullet to the brain, won’t be coughing up any clues.

But the news gets worse when the steel door to the freezer suddenly slams shut, trapping both Beckett and Castle inside. Ensuing cries for help go unanswered, and a desperate attempt to blast the lock with ammunition fails, leaving the shivering crime-solving duo with only one option: cling to each for warmth — and some major they-so-belong-together sparks. "It’s cold in that freezer," says Katic with a sly smile during an on-set break. "But maybe the heat between them can keep them alive."

Castle producers surely hope the episode, which caps an explosive two-parter that began February 21, will generate some off-screen heat as well. With a season-to-date average of 10.4 million viewers, the quirky crime procedural is such a reliable performer in its Mondays-at-10pm time slot that, in January, ABC execs gifted its cast and crew with an early renewal for Season 4. But what the show still needs — and thanks to a smart, seamless blend of mystery, romance, action and humor, deserves — is the buzz that could help it build beyond its loyal fan base to become a breakout hit. "It feels like, for the most part, people either love us or they’ve never heard of us," says creator Andrew Marlowe. "It boggles my mind that we could’ve been on for three years and there are still people out there who are like, ’What’s Castle?’"

It doesn’t help that ABC’s current schedule isn’t exactly bursting with character-driven procedurals. (The net’s other cop drama is the struggling Detroit 1-8-7.) If it were, there would be more opportunities to advertise Castle to an audience that may be predisposed to watch it. "Marketing a procedural at ABC is a challenge," admits Marlowe. "I think there are a lot more people out there who could be enjoying our show."

The normally easygoing Fillion confesses to feeling frustrated by the lack of promotional love. "I dropped 60 bucks on the lottery [recently]," says the actor, who developed a cult following thanks to roles on such buzzy series as Firefly and Buffy the Vampire Slayer. "I didn’t win. But if I did, my plan was to buy some commercials for Castle so you couldn’t watch TV without seeing one. I believe people will listen if you tell them, ’This is a good show. Get in on it.’"

Now’s certainly the time. Castle has found its groove in Season 3, striking an artful balance between the offbeat cases that have become its trademark — a scientist who may be the victim of an alien abduction! The owner of a magic shop drowned in Houdini’s water-torture tank! — and more serious-minded efforts, like this month’s two-part event, which becomes a race against the clock to prevent another terrorist attack in New York City. Heroes’ Adrian Pasdar guest stars as a federal agent who, Marlowe quips, is "the Castle version of Jack Bauer." "Initially, I’m perceived as a hardass," Pasdar explains. "My character is single-minded and driven to a point where it ruffles some feathers. But ultimately you understand exactly why he needs to get the job done right. There’s a reason he is who he is."

The formative tragedy that compelled Beckett to become a cop — the unsolved murder of her mother — took center stage in another dramatic standout that aired in January. The same episode also dialed up the sexual chemistry between the emotionally guarded homicide detective and her amateur partner when they shared a long-awaited kiss. When he read the steamy scene, which started out as a case-driven diversion but quickly turned into something more, Fillion admits his first thought was, "Wow, [fans] are gonna go nuts when they see this! Once two people engage like that, there’s no going back."

Or is there? Neither Castle nor Beckett has broached the subject of the liplock since — and still won’t, even when they face the possibility of death by freezer. "I don’t feel like that’s a cheat at all," insists Marlowe. "To confront the kiss head-on wouldn’t be true to either of the characters. She’s never been open about how she feels about anything, and he usually finds a way to joke about everything. By not doing that, you understand how important it really was to him."

While Marlowe concedes network execs have concerns about letting the pair embark on a relationship — "Everyone talks about the Moonlighting curse" — ultimately, he considers his show less a murder-mystery caper than a grand love story. Which means the answer to the eternal question of "Will they or won’t they?" is a resounding "They will." "I’m absolutely convinced there’s quality storytelling to be had after they get together," says Marlowe, who’s been married since 1997 to fellow Castle writer Terri Miller. "Anybody who’s been in a relationship knows that they have complexities and compromises. There’s plenty of stuff to mine."

For more with the Castle crew, pick up this week’s issue of TV Guide Magazine, on newsstands Thursday, February 24!