Was anything significant changed about the next-to-last episode, or only the finale?

Shawn Ryan: I'm trying to think. There may have been some minor dialogue tweaks. I can't remember what they were.

The reason I ask is that there were certain scenes in that episode — Admiral Shepard calling Grace, or the reasons why Ernie Hudson killed himself — that felt like they might have been fleshed out more in a regular episode 13, rather than the one you had to make. 

Shawn Ryan: In fact, you just reminded me. We had a whole storyline where Admiral Shepard was going to go on trial, and put a lot of pressure on Grace. Was there anything she could do from afar to try to save him? That was going to have some tragic circumstances.

Once you knew you were ending the show with this episode, how and why did you decide that Marcus would go down with the ship?

Shawn Ryan: There are a lot of choices to be made there. We felt he was someone who would go down with the ship, for whom there wasn't much left back home. And as long as there was a purpose to staying behind — in this case, to make sure that the sub wouldn't fall into Chinese hands — it felt like the noble thing for him to do. I always felt like his actions, whether you agreed with them or not, came from a place of nobility and principle, and he was someone I thought would sacrifice himself for that nobility and principle.

Well, cancellation gives you a freedom to kill your main character in a way you couldn't do if the show was continuing.

Shawn Ryan: (Laughs) It certainly does!

Was there any pause from either ABC or Sony about that decision, or did they just say, "Well, the show's ending anyway, you and Karl do whatever you want"?

Shawn Ryan: I have to say that they really let us do what we wanted from the very beginning. Any qualms that anyone has about the show can certainly be placed at my feet and Karl's feet. There was no panicky network, "Ohmigod, we've got to do this" notes. They would occasionally remind us that they were a network that was strong in female viewers, and that we should be careful that there were stories and characters that their female viewership could plug into, but ultimately, maybe we failed at that. But other than that, we said, "Here's what we want to do," and they said, "Great."

We talked about this in the summer, and Paul Lee was fairly open about this: this show was not an ideal fit for ABC's brand. Given all that, is there anything you could have done with the show — forget about quality for a second, but in terms of making it fit in more with the brand to maybe make it more successful?

Shawn Ryan: Probably. But nothing that I could have lived with creatively. In retrospect, probably the thing I could have done was sell it to NBC and have them air it after "The Voice."

Okay, so let's talk creative now. This is a show that had a lot of moving pieces, and every new show has a learning curve. In terms of making these 13 the best they could be, is there anything that in hindsight, you wish you had done a little bit differently, or better than you did?

Shawn Ryan: I think we struggled a little bit in the first couple of episodes after the pilot to find a strong, simple throughline for the story. I liked those first couple of episodes, but I didn't love 'em. I felt like we really got into a groove starting around episode 5. But by then, the ratings future was already written. Really, the ratings future was written on the pilot. When you start off at a 2.2 (demo rating), it's tough to maintain that. Yeah, I see all sorts of things I would change. It was a very, very complicated show. It was a very difficult production, being orchestrated from afar between Los Angeles and Hawaii, a very large cast, very sprawling story, and a large percentage of the 13 episodes, I would defend vigorously. And other stuff, I would acknowledge could have been better.

One of the issues I had and that a number of my readers had was the idea of Serrat continuing to exist and be out in the world, not only after he killed some of Marcus's sailors, but after he participated in a chemical attack on his own people. How did you feel the material with him worked out?

Shawn Ryan: I love the actor, and I loved him as a bad guy, and I guess you could say maybe we were guilty of falling in love with our bad guy too much, if that's the way you felt. In the third episode, he kind of lays out the case for why he feels he's untouchable by them in terms of having the people loyal to him, and death by a thousand cuts. In my mind, that was always something that lived in Marcus's head: that going directly after this guy might provide some momentary satisfaction, but might create real long-term problems at a time when they already had a very formidable episode in the United States on another flank. I guess my argument would be that Marcus, who we always played as a chess master of sorts, looked beyond the first move of, 'Oh, let me just take this guy out,' to what would the ramifications of that be, and making a more prudent move in that regards. But I understand the point you and the readers are making.

You said before that the writing was on the wall even after the pilot writings. There are a lot of industry reporters who follow the ratings who were saying, "No, the numbers aren't good, but ABC could be doing worse, and this is an audience that ABC doesn't normally reach. Maybe they might want to stay in business with this a little longer." At what point was it clear to you that this was not going to happen? How quickly did you know there wouldn't be more episodes?

Shawn Ryan: You always hope, and you see shows like "Fringe" lasting for five years, and you think, 'Why not us?' So I knew probably from episode 3 or 4 on that it was dire, but I really loved the show and maintained a lot of hope that it would continue. I didn't fluff my followers on Twitter with hopes that I myself didn't believe in. I believed that if we could solidify at a certain number, and we had some very good episodes coming up, in my opinion, and that we had a network that really loved the show — Paul Lee, creatively, really loved the show, and so did his execs, and we were on time and we were on budget, so we had a lot of goodwill over there. ABC wasn't looking to get rid of us, and Paul was a little heartbroken that America didn't discover it. I knew things were dire early on, and I just kept working and controlling what I could control.

You've been through a few of these cancellations in a row now, with this and "Chicago Code" and "Terriers." Does it get any easier?

Shawn Ryan: Listen, I have a bit of a Zen attitude about things. I try not to get too up when things are going well and too down when things aren'g going well. I tend to be more disappointed for others than I am for myself. I feel bad for the crew, who really worked their asses off, and who now don't have a job. I feel bad for the cast. In my mind, I know that I gave everything I could to the show, and I gave my best with it. I'm very proud of the show. My employers probably wouldn't like to hear this, but I'd rather be proud of a show that failed than not be proud of a show that succeeded.

Alan Sepinwall has been reviewing television since the mid-'90s, first for Tony Soprano's hometown paper, The Star-Ledger, and now for HitFix. His new book, "TV (The Book)" about the 100 greatest shows of all time, is available now. He can be reached at sepinwall@hitfix.com