"Forbidden: Dying for Love" is now in its third season. The show follows stories about various relationships that break taboos.

FORT WALTON BEACH — The case of James Flanders will be profiled again on television, more than two weeks after "Dateline NBC" documented the case.

On March 20, Investigation Discovery's show "Forbidden: Dying for Love" will unpack the relationship between Flanders and Marie Carlson, which ended in a tragic murder.

Flanders is the disgraced Fort Walton Beach pastor who pleaded guilty in April 2016 to the October 2011 killing of his "sister-wife," and mother of his infant child, Carlson. Carlson was 37 years old when her ex-husband reported her missing in October 2011. Flanders moved to Arizona shortly after the disappearance. He continued to be a suspect in the case, but there was little evidence.

"This case was particularly difficult to prosecute because there was no body, no real evidence," said State Attorney Bill Eddins, who was interviewed for the show.

Eddins said the State Attorney's Office monitored the Okaloosa County Sheriff's Office investigation, which worked for years to collect sufficient evidence.

"It's a tribute to the Okaloosa County Sheriff's Office that they continued to allocate time to the case," Eddins added. "They would not let it die."

"Forbidden: Dying for Love" is now in its third season. The show follows stories about various relationships that break taboos, said the program's showrunner Ellen Arnold. 

"This was a case that featured all of those perspectives," Arnold said in an email. "The polygamous nature of Marie’s relationship with Flanders and his wife went against the religious teachings that Flanders — a pastor — professed to follow. He was a leader in the community, somebody who was trusted and who was followed. He used his position to influence those around him, and he went to extraordinary lengths to hide the true nature of his relationship with Marie."

When Flanders admitted to killing Carlson after fathering a child with her, he took a plea deal in exchange for sharing the location of Carlson's remains. Eddins said it was a difficult decision to compromise the case. Flanders currently is serving a 15-year sentence.

"We discussed it with Marie's ex-husband and sisters," he said. "It was extremely important to recover the body and have that closure."

Arnold said they have been interested in documenting the Flanders/Carlson case since Season One, but it was only after Flanders' confession that they felt they could fully tell the story. The show includes interviews with Eddins, Assistant State Attorney Angela Mason, Jeff Carlson (Marie's ex-husband), Paris Carlson (Marie's daughter) and Daily News reporter Tom McLaughlin, who covered the murder and trial. Filming in the area took place over four days in July 2017.

Arnold said the episode will be different from "Dateline NBC" in that the focus is more on the emotion of the case rather than the investigation.

"We are telling the story of Marie's life in Fort Walton Beach in its entirety, not just the last months of her life," she said. "Among others, we interviewed Marie's ex-husband, Jeff Carlson, and her daughter, Paris, who lived with Marie and the Flanders family for some time. Paris shared memories with us, and a unique insight, of what life was like in the Flanders' home as well as precious recollections of her mom."

There's certainly interest in the relationship between Flanders and Carlson, whose romantic relationship led to a polygamous marriage. Arnold said the show will take a deeper look into the individuals and their relationship.

"Marie was a vulnerable woman who was taken in by a man who professed to care for her but who ultimately, and tragically, betrayed her," she said. "James Flanders was, by all accounts, a well-known and well-respected member of the community. Outwardly he was a man of upstanding morals and religious conviction, but behind closed doors he was somebody willing to do whatever it took to keep his secret relationship hidden.

"Allowing viewers a look behind those closed doors, into James and Marie’s relationship, is one of the many reasons why this episode is so compelling."