Michael C. Hall and Jennifer Carpenter

[Warning: This story contains major spoilers from both the previous and the upcoming season of Dexter. Read at your own risk.]

Dexter is in trooooouble!

When Dexter returns for its seventh — and penultimate — season, both viewers and their favorite serial-killing blood spatter analyst will discover just what happens when his secret is revealed.

The last we saw of Dexter (Michael C. Hall), he had finally delivered his own biblical form of vengeance upon Travis (Colin Hanks), who had left Miami in fear over where the Doomsday Killer would strike next. He had also kidnapped Dexter's son Harrison, which finally hit a nerve with the often emotionless Dexter, who then stuck it to Travis — literally — in the closing moments of the finale. Unfortunately, Dexter wasn't alone in that church, with Deb (Jennifer Carpenter) planning to profess her love to her brother before walking in on him driving a knife into Travis.

Dexter Boss on the Finale Twist: It's finally time to deal with [SPOILER!] head-on

Clearly, Deb's reaction will be Dexter's greatest obstacle this season as he's faced with someone finally taking off his mask. But his sister isn't the only person Dexter will have to worry about when evidence at the church suggests the Bay Harbor Butcher is back. Considering Dexter framed Doakes (Erik King) for that, even Deb may not be able to protect him.

TVGuide.com turned to executive producer Sara Colleton to get the scoop on the seventh season, including Chuck star Yvonne Strahovski's killer new role and saying goodbye to Dexter after Season 8.

Since the season is picking up right where we left off, just how many curse words will Deb use when the show returns?

Sara Colleton: [Laughs] It rocks her world so there are a few classic Deb-isms. If the series-long quest for Dexter was to finally have someone who really knows him — well, be careful what you wish for because Deb now knows everything and that's a game-changer.

If last season was about finding faith for Dexter, what is this season about?

Colleton: It is about things he's never experienced before, which are regret, responsibility, shame, betrayal, all of those things. Also, it's the flip side of wanting to be known, and then once you are known, there's a loss of freedom. It comes with heavy responsibility, so he's dealing with a lot of emotions that he's never had before, and never been allowed to feel before or allowed himself to feel before.

Deb only saw Dexter kill Travis on the table, but will she learn everything this season?

Colleton: Yeah. Obviously this whole season we're going to have great fun playing with every permutation that can be played between Debra and Dexter in their relationship now that this information has come out. She was on her way to the church at the end of the last season because she had come to realize that she not only loved her foster brother Dexter but she is in love with him. So now what does she do? Does she turn him into the police? Is she repulsed by him? Can she continue to love him? Does she feel an odd relief that finally she understands some fundamental part of him that always felt elusive? Dexter was always elusive and Debra always thought it was because of her, and now she knows it wasn't about her, it was about him really protecting her.

But she is the head of the homicide division and so it has to really affect her sense of justice and the whole system. It's a really challenging year for her to juggle. And Dexter, of course, his world is equally rocked. He's never had to deal with these kinds of emotions — regret, guilt, a sense of having let Deb down and also, obviously, the gnawing suspicion that at any time, she could have him arrested.

VIDEO: New Dexter trailer teases Deb's reaction

Given what Deb learns about Dexter, how will that change her sudden revelation that she has feelings for him?

Colleton: It will be explored. It has to explored, because one doesn't come to a realization like that and then completely change. But obviously what she learns is going to affect it, so all of the things that have been the bedrock of Deb's life get moved around. That's part of what we hope will be fascinating for our fans, is to watch and see how we play out all of those various interpretations.

Will we see a vulnerable side to Dexter this season?

Colleton: Oh, yes. It is like Superman's cape has been taken off. He's extremely vulnerable and that is very interesting to see and to explore.

Is there a sense of relief knowing if he'd let anyone in like he did with Lumen (Julia Stiles), he'd want it to be Deb?

Colleton: I think that's part of it because [the relationship with] Lumen was certainly almost like acting out for his guilt in Rita's (Julie Benz) death. But Deb has been the rock in his life from the time he was taken in by Harry. I always go back to one of the very first scenes in the pilot when he goes, "Oh that's my foul-mouthed sister Deb and if I could love anyone it would be Deb." They have had an incredible closeness. So that, in some ways, is a relief, but it comes with a whole new set of responsibilities.

Speaking of Harry (James Remar), he's always helped Dexter with his Dark Passenger, but now that Dexter's issues involve Debra, how will his advice to Dexter differ from what we've seen before?

Colleton: It's very upsetting to Harry. For Deb, she's always suffered from feeling like Daddy's second best. She realizes now, too, that this was never her being second best. She will learn all about Harry training Dexter and that is another thing that is going to rock her world. Again, in the pilot, when Harry tells Dexter that people deserve to die, and [in Season 5], when Deb hated Jordan Chase (Jonny Lee Miller) and she says, "Maybe there are people who deserve to die." It's a very complicated year on that level. We're really enjoying exploring all of these things because now it's all out in the open.

What other obstacles will Dexter face because of Deb's discovery?

Colleton: There are other complications that will come in because, at the crime scene, Dexter's blood slide gets found by Lieutenant LaGuerta (Lauren Velez) because he loses it in the chaos that ensues and she immediately recognizes it's his. The only other time that she had seen this blood slide was in the copy case of the Bay Harbor Butcher. Her dear friend Sergeant Doakes, everyone thought he was the Bay Harbor Butcher, and thought that when he died, the Bay Harbor Butcher died with him. Now, she begins to suspect, "Is the Bay Harbor Butcher still alive and how can I set about proving the innocence of my friend Sergeant Doakes?" That is something that's a silent thing at the start, but it's, again, going to be eventually working its way back to Dexter. It's going to be very interesting to see if she can exonerate him.

What can you tell us about the new castmembers?

Colleton: We have Ray Stevenson, who — oh my God — he is such a fantastic actor. He plays the head of a crime syndicate who owns many nightclubs in Miami. Jason Gedrick plays George, the U.S. manager of all of his clubs. Ray Stevenson's character, Isaac, comes to Miami when his very close personal lieutenant is accused of killing a Miami cop and then suddenly disappears. So Isaac wants to find out what happened to his friend and how he disappeared. The fact that it was a cop will bring them all around the Miami Metro police system. That is going to be a long story arc.

Also, we have Yvonne Strahovski. She is fantastic. She plays this woman named Hannah, who took off from this small rinky-dink Florida town and ran off with this older guy and they went on this wild killing spree. So when they got caught, she turned state's evidence on the boyfriend, he went to jail for life and she started a new life. Years later, she's in her 30s and she will intersect with Dexter. I would say Hannah is a still water that runs very deep and is quite unlike any woman Dexter has ever known.

Chuck Star Yvonne Strahovski joins Dexter

How does Hannah compare to Lumen? And is there a possibility of a romance transpiring between Dexter and Hannah?

Colleton: There's always the possibility. Whenever there's a man and a woman, there's always that possibility — or a man and a man or a woman and a woman or any configuration. There's nothing needy about Hannah. Every woman that Dexter's ever come to either the rescue of or been involved with have been incredibly needy. Lila (Jaime Murray) was one of those borderline women who other women take a look at and say, "Stay away!" but men can never resist them. You just know that they are bad news. Rita was damaged goods just like Dexter. And Lumen, when she appeared in his life, she was severely damaged. Hannah has a cool aloofness, but there's something about her that will intrigue him.

Since the show has been renewed for two more seasons, is this definitely the end?

Colleton: This was definite. We wanted to end it this year, but the network convinced us that it would be best to do it in two years. In some ways, this is a two-season series-ender. We have worked that out and know where it's going to end. Next year will definitely be the last year of Dexter. Absolutely.

Are you guys ready to say goodbye to Dexter?

Colleton: From the very beginning, when I first started developing the pilot, I always knew it would be a seven-year arc for this series. I feel easily that we can be an eight-year show, but I never want it to get old and stale. I want us to go out on a high and everybody on the show is determined to keep the level of it up to the very end. It's always wise to know when it's time to leave the stage before you're asked to leave the stage.

Do you think Dexter has to die at the end?

Colleton: [Laughs] I would never answer that question.

Do you know what the final scene is?

Colleton: We don't know what the final scene is, but we know where it's going. We know now exactly how it's going to end and how the series will end.

How do you think Dexter should end?

Stay tuned for more Dexter scoop in our weekly Mega Buzz column.

Dexter returns Sunday, Sept. 30 at 9/8c on Showtime.