Is 'Under the Banner of Heaven' Based on a True Story? Yes, and No

FX's new show, Under the Banner of Heaven, might be a true crime story, but it also contains some fictional elements that fans may not notice at first.

The drama, which is led by Andrew Garfield, examines the 1984 murder of Brenda Wright Lafferty and her 15-month-old daughter, Erica.

Here is everything you need to know about the show, what is real and what has been created for the benefit of the story.

Is 'Under the Banner of Heaven' a True Story?

Under the Banner of Heaven is split into three storylines, Detective Jeb Pyre's investigation into Brenda's death, Brenda's life and marriage into the Lafferty family, and the creation of The Church of Jesus Christ of Latter-day Saints (LDS).

The first follows the real-life tragedy that befell Brenda and her daughter, a murder that really happened and shocked the nation.

While their deaths did take place, elements of the investigation have been fictionalized for the purpose of the FX show. Both Garfield's Detective Pyre and Gil Birmingham's Bill Taba were created especially for Under the Banner of Heaven—they didn't really exist.

When asked if they based their characters on anyone, Garfield told Newsweek jokingly that they "were ghosts," so they didn't feel the need to, but he did speak with a Mormon detective who wished to remain anonymous.

Birmingham added that they wanted to bring an "authenticity" and "honesty" to their roles, even if their characters didn't actually exist: "[We wanted a] truthfulness in telling the story to honour the people that were murdered and to maybe bring some humanity to a very dark material and how people can relate to just, this could be any of us.

"And how just being introspective or reflective about the characters and watching them, and how they evolve and bond, can give you hope that we can be better people."

The investigation itself is real and did lead to the arrest of Ron and Dan Lafferty (Sam Worthington and Wyatt Russell), brothers of Brenda's husband, Allen, who were responsible for her death and believed they had received a revelation from God to kill her and others.

The show's second storyline, which focuses on Brenda's life, and her time with the Lafferty family before her death, is also true and it draws on Jon Krakauer's nonfiction book Under the Banner of Heaven for its anecdotes.

Series creator Dustin Lance Black also told Newsweek he worked closely with Brenda's family to understand what she was like, so that he could best portray her in the dramatization of the events.

Dustin Lance Black on Adapting Jon Krakauer's book

Black grew up in a Mormon household, and this is why the show also has an accurate depiction of the creation of the LDS church, its founder Joseph Smith and his wife Emma Hale.

The show took 10 years to go from script to screen, and Black explained that this was because his original plan of adapting the story into a film proved too difficult.

"For a drama, let's be real, people don't want more than two hours these days, and two hours I found, time and again as I was trying to crack the story, in a feature screenplay format, it's not enough time," he said.

"It's not enough time to tell all of the Lafferty story from 1979 to 1984, all of the investigation story, that 10 days it took to solve this crime, and the Mormon history that helps us understand both of those stories.

"I needed all of that to, in a way, create an experience that reminiscent of the readers experience with Jon Krakauer, his book."

He went on: "I wrote some really terrible, very long, screenplays for many years and thankfully, Ron Howard and Brian Grazer [the show's executive producers], were very patient, and eventually the limited series would come to be a legitimate form again.

"So, I had set it aside to do other things for a little while but when I picked it up again I had many more hours, and then I think there was room to attempt this thing I've attempted.

"To tell these three stories that all take place in one man's mind that I hope recreates that very active experience for the viewer in the way that the reader experienced the book."

Under the Banner of Heaven airs Thursdays on Hulu.