“I thought I could change what I am. Keep my family safe. But it doesn’t matter what I do, what I choose. I’m what’s wrong. This is fate.”

Those were Dexter Morgan’s last words to the viewer in the jaw-dropping fourth season finale of “Dexter.” Poor Dexter had danced with his biggest foe and allowed himself the possibility of becoming a better man. Instead, the truth revealed itself in his wife’s pool of blood: Dexter Morgan can’t be anyone but who he is.

The shocking twist — Rita’s death and what it means for Dexter — places Showtime’s highest-rated series at a compelling crossroads for its fifth season premiere on Sunday. Are viewers to accept once and for all that Dexter is a hopeless sociopath/avenging angel who will never be as human as we’d like him to be? Or will the tragedy prove transformational?

“The rug is completely pulled out from under him,” said Michael C. Hall, who has received three Emmy nominations for his portrayal of Dexter. “And all bets are off at that point.”

Since viewers first met the blood-spatter analyst and serial killer of serial killers, Dexter has insisted that the capacity to have real emotions eludes him, even though much of last season he struggled to counter his “darkness” by being a loving husband, father and brother.

Dexter also spent last season painstakingly stalking fellow serial killer Trinity (John Lithgow). After killing Trinity, Dexter celebrated in the moonlight, fantasizing of a life with Rita ( Julie Benz) and their three children without his “dark passenger” (as he refers to the darker side of himself). But when he arrived home, he found that he had been outplayed — Trinity had already murdered Rita before Dexter got to him, leaving all hopes for a bloodless future dashed.

“I’m sure Dexter wishes he could go back in time and kill [Trinity] in the most merciless way he can imagine,” Hall said. “But it’s too late.”

On the Hollywood set, the people who pulled off last year’s best-kept TV secret are still being quite coy. During a quick break while filming a scene in Dexter and Rita’s house for the ninth episode, Hall jokes that he feels like Dexter’s press secretary. “I answer questions at length without saying anything.”

The scene being shot between Hall, guest star Julia Stiles, and the young Christina Robinson, who plays Rita’s daughter, Astor, doesn’t give away much. Astor is angry with her stepfather; Dexter, as usual, is clueless; and Lumen (Stiles) seems concerned. To reveal details of Stiles’ first TV role would ruin a surprise that comes early in the season.

“Lumen has experienced a lot and has been very traumatized and damaged by the time Dexter meets her and is having a very hard time moving past that,” said Stiles, trying to describe her. “And she and Dexter have this strange connection, which poses problems for Dexter because obviously he leads this double life.”

Dexter’s personal life isn’t the only thing about this Emmy-nominated drama that’s turned upside down. Executive producer Clyde Phillips and co-executive producer Melissa Rosenberg resigned at the end of last season at the show’s height of success. “Dexter” earned seven Emmy nominations and averaged 4.7 million viewers last season, a 41% increase, and ended with a riveting episode that registered nearly 6 million viewers.

“It’s a tough act to follow — that season,” said new executive producer Manny Coto, who worked on “24" for five seasons and was hired on “Dexter” by new show runner and executive producer Chip Johannessen, who also worked on “24.”

The new producers faced the daunting task of moving creatively beyond Dexter’s new reality and accepting that they probably couldn’t conceive of villains more memorable than the ones that had challenged Dexter in the third and fourth seasons — Miguel, played by Jimmy Smits, who was nominated for an Emmy; and Lithgow, who won an Emmy for his portrayal of the chilling Trinity Killer.

“That season hemmed us in a little bit,” Johannessen said. “What we wrestled with mostly is the replacement for his wife, because now we do have this pulp thing of a lone wolf and cub image, which is not accessible in the same way that a suburban family is.”

After weighing several plot lines, the writers decided to begin the season exactly where the story concluded, with Dexter’s gruesome discovery.

“We felt there was an emotional residue that needed to be dealt with in the wake of the death,” Coto said. “And to skate past that would to be rob the audience of Dexter’s reactions to what happened and how he gets his life back together.”

Instead of focusing Dexter’s grief-stricken attention on one single serial killer this season, the writers opted to introduce several characters that cross paths with Dexter at different times but will connect in surprising ways as the story line progresses.

“If there’s a killer he’s after, maybe it’s himself, in as much as he’s contending with the fallout of what turns out to be irresponsible indulgence in his relationship with the Trinity Killer,” Hall said. “It led directly to his wife being murdered and the whole structure he built for his life being dismantled.”

Stiles appears in nine episodes, but there are other shadowy figures who pop up: Boyd, a peculiar dead animal retriever (“Southland’s” Shawn Hatosy); former cop Stan ( Peter Weller of “RoboCop”); and life coach Paul (Johnny Lee Miller of “Eli Stone”).

“There’s not one bad guy but a cascading group of guys that gets bigger and bigger,” Coto attempts to elaborate. “But there’s one element that carries him through the season, and that’s Julia Stiles’ character.”

With only three episodes left to produce for the season, Hall, also an executive producer, said he was feeling exhausted and was waiting for “a second wind to hit.” His bout with cancer behind him, Hall looked fit and healthy and was as enthusiastic about playing Dexter Morgan as he’s ever been.

“What’s wonderful about this is that I’m in the fifth season of a television series, and it is arguably as challenging and as compelling as it’s ever been for me as an actor — just because of the way the character has evolved and been forced by circumstance to move forward in ways that neither he nor I ever anticipated when we started,” Hall said.

maria.elena.fernandez@latimes.com