Given the outlandish and bewildering nature of the allegations made against NXIVM, the New York-based "self-help group" co-founded by Keith Raniere and Nancy Salzman in 1998 that ultimately served to recruit women for a sex cult that included high-profile members like Smallville actress Allison Mack, you might expect HBO's new documentary series The Vow, which debuts Sunday and digs deep into the notorious Hollywood-adjacent case, to be similarly salacious and shocking in nature. But the nine-episode series, directed by Oscar-nominated husband-and-wife team Karim Amer and Jehane Noujaim, is less concerned with sensationalizing an already unbelievable story than it is examining and explaining how seemingly sound-minded individuals came to be part of a cult and under the influence of a man like Raniere.

For this reason, the docuseries, of which seven episodes were sent to critics for review, is a fascinating, but not exactly exciting, addition to the documentary slate. It takes time for the series to get around to discussing the most exploitative aspects of the organization, including Dominus Obsequious Sororium, known as DOS or The Vow, the secret all-female organization within NXIVM (pronounced nex-e-um) that was at the center of the most horrifying acts that allegedly took place, including branding "sex slaves" with Raniere's initials and using "collateral" — which could be private information, embarrassing confessions, or even nude photographs — to blackmail women into submission and silence. But by building a foundation of knowledge and carefully shedding light on the events that eventually led up to the blistering 2017 New York Times exposé that made NXIVM and its leader front page news, the filmmakers are able to build a sympathetic narrative for their subjects that explains how something as unbelievable as this story could happen. 

Mark Vicente and Sarah Edmondson, <em>The Vow</em>Mark Vicente and Sarah Edmondson, The Vow

Most episodes of The Vow more or less highlight a single subject, beginning with South African-born filmmaker Mark Vicente and Canadian actress Sarah Edmondson, both formerly high-ranking members of NXIVM who have become the loudest voices against it and appear prominently through the series. Their stories reveal how their relationships with Raniere and NXIVM came to be and how they evolved over time through Executive Success Programs, or ESP, a company beneath the larger NXIVM umbrella that was pushed as a tool for success and self-empowerment. And while both initially seemed to flourish in NXIVM — Edmondson, in particular, was incredibly successful at recruiting members into the organization — it eventually becomes clear that the expensive workshops and programs the company put on are what allowed Raniere and some of his high-ranking deputies to methodically prey on men and women who were looking for self-fulfillment and use their "weaknesses" against them.

End your browsing nightmare with TV Guide's recommendations for every mood

The series, using a surprising amount of footage from NXIVM events and interviews — likely provided by Vicente, who was the organization's de facto videographer, though it's never outright confirmed — paints Raniere as unimpressive, unimposing, and also a bit of a dork. There's extensive footage of him dressed for indoor volleyball, sweat headband and protective knee pads and all, which isn't exactly what you picture when you imagine the head of a cult, sex or otherwise. But Raniere intentionally taught people to ignore their gut instincts so he could more easily groom and influence them as a means to strip away the things that had made them happy and replace them with his teachings under the guise of becoming better versions of themselves. He pushed his brainwashing techniques as growth and character building, which is alarming on its own but is made even worse when it's later revealed several women in the company's upper echelon, including Lauren Salzman, the daughter of NXIVM's co-founder, used them, along with the promise of female empowerment, in order to groom impressionable young women as sexual partners for Raniere. 

While not every woman in DOS was engaged in a sexual relationship with Raniere — Edmondson never was — Salzman and other "masters" in DOS used his means of emotional manipulation and sleep deprivation to break down the will of their own "slaves." At one point, a young woman known only as "Jane" revealed that she had to ask permission any time she wanted to eat, which was the group's way of controlling her weight. She also had to be available at all times, day or night, and was required to keep daily lists of everything she "failed" at that day, a form of self-inflicted punishment that was said to help her break through her barriers and become the perfect version of herself. 

Sarah Edmondson, <em>The Vow</em>Sarah Edmondson, The Vow

Most viewers will likely tune in to The Vow hoping for obscene details about the sex cult that brought down an actress from Smallville or to find out how Raniere's case turned out (in 2019, he was found guilty of sex trafficking, racketeering, conspiracy to commit forced labor, and other felony charges and is currently awaiting sentencing). But the most compelling aspect of the docuseries is its thorough and unflinching examination of the different methods Raniere and his deputies employed to manipulate and brainwash people. As chilling as the revelations in the series are, they help us better understand how something as bewildering as this story can happen.

At the end of the fourth episode we see footage of Raniere's first meeting with Mack, who was said to be one of the top members of DOS and was identified by Edmondson as the person to brand the women of the group. In that intimate and unguarded meeting, viewers can see how easy it was for Raniere to convince Mack that the thing that had made her happy — art — in fact did not make her happy, that what she felt was not real, and that he held the wisdom that could lead her to complete happiness. "The most excitement you've ever felt is yours to have all the time," says Raniere. "If you feel that art is necessary for that, that's almost a self-condemnation." Mack, who in 2019 pleaded guilty to charges of racketeering, sheds tears during the meeting, and it's alternately sad and horrifying to watch her be manipulated, knowing she would later rise up the ranks of NXIVM herself and use similar techniques on other women. 

No one ever thinks they'll become the victim of a cult or be brainwashed, but The Vow reveals just how easily it can be done when someone knows how to do it, and that is almost as horrifying as anything else depicted in the documentary, which is saying a lot.

TV Guide Rating: 3.5/5

The Vow premieres Sunday, Aug. 23 at 10/9c on HBO.