With TNT's long-running series "The Closer" winding down to it's series finale next year, there's no doubt which other cable hit is gunning for its spot as the most-watched cable series. "Rizzoli & Isles," which started strong out of the gate when it premiered last year, has been nipping at the heels of Kyra Sedgwick's procedural drama in terms of the ratings and has also been performing so well this summer that TNT recently gave the Angie Harmon/Sasha Alexander starrer an early order for a 15-episode season three that will air in 2012.

To find out more about the initial casting of leads Harmon and Alexander, how closely the series is sticking - or not sticking - to the Tess Gerritsen books as well as a few teases as to what is coming in the rest of season two, our Jim Halterman chatted with series creator Janet Tamaro last week.

Jim Halterman: The chemistry between Angie and Sasha is the stuff that TV shows live and die by. Did you see that chemistry from the start?

Janet Tamaro: Yes! Once we had Angie attached, we knew we had a show but trying to find someone who would come in as a different flavor, not the same physical type and who could hold the screen the way she could hold the screen was a hard thing to do. In the books, Dr. Maura Isles has dark hair, is sort of Morticia-like and is nothing like Sasha Alexander or anything like this character that I developed. It works beautifully in the book but it wouldn't work well in television because of the dark hair, pale skin and Tess Gerritsen will be the first to tell you, there's no humor in the book and I really wanted to do something that smashed together that dark/light thing that happens in life when you have a job like a homicide detective or, like me, I was a reporter and I covered all sorts of really gruesome crimes.

JH: How did you end up with Sasha?

JT: I think we saw every available actress who was interested in doing television... and then I watched tape on Sasha and loved that 'want' she has and thought 'Oh, it doesn't fit this dark medical examiner at all but there's something really lovely about her.' We couldn't get her into test because she wasn't interested at that point in coming back to doing a series. She was getting work but we finally coaxed her in and put her in a room with Angie and it was KABOOM! It was absolute magic and they made each other laugh and they immediately hugged and it's like the new girl starting at school and spotting the girl who is going to be her best friend.

JH: There is a clearly a darker layer in the series since this is a crime drama and there are murders to be solved but how much of a challenge is it to balance that with the lighter side?

JT: I should probably tell you it's harder than it is for me but it's naturally where I go and it's where I went as a reporter when I was in the middle of covering really disgusting stuff. If you hang around cops, they have this very dark sense of humor and, not only that, life goes on. You forgot your dry cleaning, your shoes hurt, you wish that guy had called you back... for me, it was hard to convince other people that the show would work if we did that but for me it was a very natural way of getting through the darkness of life. We all have dark and light and there's no perfect day, at least in my experience.

JH: The story of Jane with Hoyt (a serial killer played by Michael Massee) is her dark, Achilles heel that you've gone back to frequently in the series. Is that going to be a thread throughout the entire run?

JT: Actually, something very cool is going to happen at the end of the summer with Hoyt. All I can tell you is that it was a cathartic episode to write because I've also been living with Hoyt for two full years. Something interesting happens there.

JH: Thank you for that tease! So, because Jane has Hoyt in her life, what is that dark thing for Maura?

JT: The darkness in Maura's life is her mobster father and that is not from Tess's books. That's just a storyline I wanted to do. One of the stories I did as a reporter was Whitey Bulger, which always kind of fascinated me, so we came up with this idea that her biological father is a mobster. The actor who plays him is brilliant - John Doman - and he will be back twice this season so that's the dark secret and source of pain in Maura's life.

JH: So you are moving away from Tess's book when you create a lot of these characters, right? Even Jacqueline Bisset as Maura's mother is not what I would have imagined.

JT: I've laughed about this with Tess. In the books, Maura's mother is a serial killer who gave up twin girls, one of them was Maura, and Maura discovers serial killer mother when she finds her dead twin. Frost (Lee Thompson Young) is a married white guy... you have to, as a television writer, make them your own because then what's the point? Some of my viewers have gravitated to the books and some of her readers have moved to the series. I only get the occasional 'Why did you... !?' I'm a massive reader myself and it occurred to me that I can't compete with somebody's imagination and what I had to do was just create characters because I'm a television writer.

JH: Since Maura is a medical examiner, is it a challenge to get her involved in the action outside of her lab?

JT: It's a massive challenge. You know, the money is when those two are together and we love to see that odd couple. My background is as a reporter and I did my homework and know what happens in the real world so I do my very best to make it part of the storyline or attach it to something like 'Jane needs a ride' but I need Maura in those scenes. I think we don't want to just see her in the autopsy room or in her office so, yeah, she comes along when it feels appropriate and she comes along even when it's not completely appropriate and I try to keep it as seamless as possible.

JH: Last week's episode had Richard Thomas and Jacqueline Bisset and earlier this season you had Ernie Hudson pop up. Talk about bringing in these guest actors.

JT: I feel like we've had a really wonderful response from actors out there. I like casting against type and bringing in an actor like Colin Egglesfield who always plays a hunky romantic lead and dirtying him up and making him the bad boy brother. I think that that's fun as an actor to not just get offered the same kinds of roles. Jacqueline Bisset is a gorgeous actress and getting her to play the cold mother was interesting to her. We have a wonderful casting director so it's been good.

JH: You, Angie and Sasha are all very present on Twitter. How much of an impact do you think social media has on the success of your show?

JT: I think it does make a difference. I think the technology is there but, on the other hand, it is the road to madness because you can read a lot of incorrect, mean-spirited things. I don't think it's any different from back in the day, I'm told, when truckloads of letters would show up and somebody would answer those letters. It would be a mistake for me as a creative person and as a writer to listen to four million people - we have nine million viewers but a certain percentage of them are on Twitter - but ultimately I have to listen to myself. But I think it makes them feel [good] because it has turned into an interactive experience and they do feel like, 'They listen and they care that I care about their show!' I love that all these people love this show and that's why you work as hard as you do because you hope someday people will respond to your writing.

"Rizzoli & Isles" airs Mondays at 10:00/9:00c on TNT.