Over three seasons of ABC’s CASTLE – which returns for its fourth season on Monday, September 19 – we’ve seen Nathan Fillion’s wealthy, best-selling mystery novelist Rick Castle fall for Stana Katic’s Kate Beckett, the dedicated NYPD homicide detective Castle follows around.

Initially, Castle’s ride-alongs were for research, but by now everybody recognizes there’s a greater investment there than just getting the facts right. In Season Three, Beckett got a lead on the cold case murder of her own mother, which unveiled a conspiracy involving Beckett’s police captain, Ruben Santiago-Hudson’s Roy Montgomery.Montgomery died heroically, protecting Beckett, but at his funeral, Beckett was shot by an unseen assailant. The season finale ended with Castle holding a possibly dying Beckett in his arms and finally saying he loves her.

CASTLE fans are eager, to put it mildly, to see what comes next. Executive producer Laurie Zaks, who has been with CASTLE since its development phase, took some time to tell ASSIGNMENT X what she can without giving too much away.

ASSIGNMENT X: How do you feel about embarking on Season Four of CASTLE?

LAURIE ZAKS: It’s very exciting.

AX: Did you know that you had a Season Four before you guys decided on the cliffhanger that ended Season Three?

ZAKS: I don’t remember the exact timing. We did find out about Season Four very early. I heard rumblings of this very early on in the year. It was percolating and evolving. But I honestly don’t remember the exact timing. If we knew the show was going to end, it would have been a different [season] finale.

AX: As Castle has just seen Beckett get shot, is he going to be a little more wary of getting his heart broken because she may die in the line of duty, or is he pushing forward with the relationship?

ZAKS: Well, I think he’s going to be very aware of the fragility of relationships and I think that, like any person would be affected by [seeing] someone they love [suffer a potentially fatal injury] – and that’s what this year is, it’s the next step in Beckett and Castle’s relationship.

AX: Can you say where Season Four picks up time-wise in relation to the end of Season Three?

ZAKS: It picks up right after the [shooting]. The first scene is in the hospital. They’re bringing her in. So it’s as fast as it would take to get there.

AX: Were there any things that happened in third season that made you go, “Oh, maybe we should go a little more this way or a less that way going forward,” especially regarding the mystery surrounding the death of Beckett’s mother?

ZAKS: That whole mythology was spearheaded and written by Will Beall, who sadly is not with us this year, because he has so many films going on, but he had this in his mind all year, that it was going to start off in one place and end in another place. And I don’t believe that storyline is over with. I’m being a little vague with these questions because there are things that will be revealed in the premiere episode that will show, or given an indication of, how Beckett and Castle’s relationship will evolve to the next step.

AX: Was the decision to kill off Ruben Santiago-Hudson’s character, Captain Roy Montgomery, based on the fact that you needed the stakes and the consequences to be really high, or did Ruben Santiago-Hudson have another job?

ZAKS: No, no, no. We’re still so very sad about [the loss from the cast]. It was all part of the storytelling. Somebody had to go and the story was so intricate and it was such a surprise, this build-up into who the third cop was. It was not another job [for Santiago-Hudson]. We were all very sad. I’ve said before, I could never have been on LOST. It was very emotional. I could never take it if all the characters were getting killed off. We’re a very close-knit group.

AX: Had you worked on a show where a character had gotten killed off before?

ZAKS: I’ve been on a show with certain contract disputes [laughs], but honestly, most of my history is in comedy. This is the first show I’ve ever developed and been the executive producer on. I came from the network side. It’s different when you’re on the other side of those negotiations [laughs].

AX: Might Adrian Pasdar’s FBI agent character be back?

ZAKS: The character was great, we all loved him, and who knows, maybe this year.

AX: Penny Johnson Jerald, who played the First Lady on the first three seasons of 24, is a new series regular for CASTLE starting this season. Who does she play?

ZAKS: Gates. She’s the new [police] captain. And that sets up a very interesting dynamic, because all of a sudden, it’s a woman working for a woman, and all of a sudden, Castle has to answer to somebody who’s not so crazy about him, doesn’t want him around, doesn’t think he’s such hot stuff [laughs].

AX: Were you a fan of hers from 24?

ZAKS: Yes. And from LARRY SANDERS.

AX: Did her work on those shows make you feel like she was the right person for this?

ZAKS: We saw quite a few people. She had all the right elements, the right amount of gravitas, great acting credentials, a sense of humor.

AX: Was Gates always written to be a woman?

ZAKS: Yes.

AX: And always African-American?

ZAKS: No. We saw everybody. It was cast totally color-blind. It was going to be a woman, but we saw all ages, all ethnicities, some wonderful actresses, but it really had to be just the right actress, and she just came in and she was great. She was everybody’s choice.

AX: And in third season, we saw Castle’s mother Martha decide to start an acting school. Are we going to see Martha giving acting lessons this season?

ZAKS: I think so. In the [fourth season’s second] episode, she is dressed up like Desdemona because she’s going to be teaching Shakespeare. We will be alluding to it, certainly. In terms of how many shows we’ve done, we do have her getting ready to give some [acting lessons].

AX: Any upcoming guest stars you can announce right now?

ZAKS: We haven’t booked any yet. There are a few juicy parts. We’re doing a GHOSTBUSTERS episode and I personally would love to book one of the original Ghostbusters, but there’s nothing in the script yet. So there are some really good parts coming up that we have to put some really interesting actors in.

AX: Are you continuing the poker games, where we see Castle hanging out with real-life mystery writers playing themselves?

ZAKS: You know, we don’t have one set yet. I hope so. I love those guys. Those guys are so telegenic. I’m always so surprised when I meet them. They get in front of the camera and they’re great. Dennis Lehane – I was just watching THE WIRE and he was on THE WIRE. He’s such a brilliant writer, he’s amazing. And Michael Connelly is a total ham, he’s totally serious when you meet him. We love those guys. I just email them. We don’t even call the agent – I just email them and say, “Hey, want to play poker?” “Sure! Tell me when I have to be there.”

AX: And did you do Comic-Con this year?

ZAKS: I did.

AX: How do you like being a rock star?

ZAKS: I loved it. Well, Nathan’s the rock star. I was just kind of standing on the side, but it was great. I loved watching Nathan and my cast being rock stars, absolutely.

AX: And is the executive producer composition of CASTLE still the same, you and series creator Andrew Marlowe?

ZAKS: I’m a non-writing executive producer. Andrew Marlowe is the creative head, show runner/executive producer, and his number two is David Amman, who’s also executive producer, and Rob Bowman is the executive producer/director. So the four of us together cover everything. I’m the only girl [laughs]. So I’m the official cast mom/writer mom.

AX: Anything else you’d like to say about CASTLE right now?

ZAKS: We hope everybody tunes in for our season premiere. It’s fantastic. It was quite a big show to come back from and Andrew did a great job. Andrew wrote the first episode. I think a lot of questions will be answered and nobody will be disappointed.”

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