HBO has struck viral gold over the last couple of years with true crime documentaries. “The Jinx” and “Beware the Slenderman” have captured national attention through taut storytelling and intensely uncomfortable subject matter. Erin Lee Carr’s documentary “Mommy Dead and Dearest,” which made its world premiere at South by Southwest on Saturday, should be the next hit in line at HBO. But unlike “The Jinx,” which slowly revealed the pieces of a mystery, leading viewers through the story with tiny breadcrumbs, “Mommy Dead and Dearest” gets the big reveal out early, and the rest of the story becomes a stacking of atrocities.

Carr, whose first documentary feature also focused on true crime, became obsessed with the story surrounding the death of Dee Dee Blanchard when she first read about it. And it’s hard not to be. Blanchard and her daughter, Gypsy Rose, were Hurricane Katrina evacuees who ended up in Springfield, Missouri. The opening of the movie shows the interview room where Gypsy Rose, with a squeaky voice and clenched posture, answers questions about the role she and her boyfriend had in the murder of her mother.

But the accusation seems absurd when the film flashes back six years to archival footage of Gypsy Rose and her mother on local news, as the community  celebrated the courage of the young Gypsy Rose, who used a wheelchair. The child allegedly suffered from multiple sclerosis and a slew of other illnesses, including a mental development disorder. How could this meek child have killed her mother?

Because that is not who she really was.

Gypsy Rose’s friends and the entire community were in shock when they saw Gypsy Rose walk into court following the slaying. A girl who had always been seen as helpless and powerless was now being exposed as possibly a cold-blooded killer. As one law enforcement official told the public at a news conference, there are a lot of things that weren’t what they seemed at the Blanchard household. Using interviews with Gypsy Rose, law enforcement and family members, Carr details the twisted history of Blanchard and the control she exerted over her daughter.

After leaving her husband, Blanchard created a life for her and her daughter that was built on lies and manipulation. Blanchard convinced her daughter that she was sick, and she controlled her constantly, through direct and indirect pressure. Not only did Blanchard manipulate Gypsy Rose (the name seemingly fit for a Cabbage Patch doll, a disturbing irony), she convinced the medical community in Springfield that her daughter was plagued with a variety of illnesses. She had a feeding tube inserted into her daughter’s stomach, took her to the hospital more than 100 times over a 10-year period for exams and surgeries, and pumped her full of prescription medication that ended up manifesting in symptoms that Blanchard then pointed to as evidence of Gypsy Rose’s illnesses. Gypsy Rose, as one medical official says in the film, was an obvious victim of Munchausen by proxy.

Gypsy Rose eventually found solace in a boyfriend she met online, but her relationship with that obviously troubled young man took on some dark overtones of its own, including BDSM fantasies and dangerous role playing. But Gypsy Rose still found comfort in his companionship. It is unclear whether Gypsy Rose wanted to kill her mother or whether her boyfriend concocted the plan and she went along with it, but after hearing the tower of evidence, one begins to understand why Gypsy Rose would go to any length to get out of the situation in which she was imprisoned. While one can empathize with Gypsy Rose and understand her motivation, it is impossible to make sense of how so many medical officials could blindly go along with Blanchard’s unsubstantiated claims.

Blanchard’s sickness and complete lack of regard for her child is one of the more disturbing stories you will see detailed on film, and Carr’s ability to win a very eloquent and self-aware Gypsy Lee’s trust helps make for candid and shocking testimony. Of course, the biggest unanswered question is how someone whose role should be of protector can turn out to be such a horrible monster. Family members describe Blanchard as evil, but it’s clear she was also the victim of some abuse in her younger life. Monsters aren’t just born; they are created. Instead of giving answers, the documentary delivers mostly sadness and horror.

After the movie, Gypsy Rose’s father, who, along with his wife, appears in the movie as vulnerable and heartbroken, said he was not pursuing medical malpractice suits against anyone in the medical community, but some in the audience and one of the film’s producers on stage at the screening stated they felt someone needed to be held accountable. The mystery in “Mommy Dead and Dearest” is less about who did what and why but how an entire community could let Gypsy Rose fall through every crack imaginable.

“Mommy Dead and Dearest” airs May 15 on HBO and screens again at 7:15 p.m. March 15 at Alamo South Lamar.