Sister Cathy Cesnik, whose unsolved 1969 murder is explored in the Netflix documentary series “The Keepers,” is pictured with her father, Joseph Cesnik. (Netflix)

A renewed fascination for true crime and unsolved mystery stories — particularly in serialized formats on podcasts and boutique TV — has taken us to deep, dark places that traditional journalism used to avoid, sometimes on legal advice. Old rules about accusing someone of a crime and jumping to conclusions have grown a bit fuzzy as a more “Scooby-Doo” approach meanders and occasionally blunders or supposes its way into new details, dramatically playing up potential evidence. Audiences are understandably engaged by this invigorating spirit of transparency.

The heroic amateurs who sleuth around in Netflix’s absorbing and emotionally gripping documentary series “The Keepers” (streaming Friday) are two unassuming women in their 60s, Gemma Hoskins and Abbie Schaub — good Catholic girls who were classmates at Archbishop Keough High School in Baltimore almost 50 years ago and have always wondered about the circumstances surrounding the disappearance and murder of their favorite teacher, Sister Cathy Cesnick, a 26-year-old nun.

On a Friday evening in November 1969, Cesnick left the apartment she shared with another nun, planning to run some errands. Her haphazardly parked car was found the next day, but it was another eight weeks before her bludgeoned, decomposing body was discovered on the hillside of a vacant lot.

Although Baltimore journalists over the years have taken pretty good swings at shedding new light on this unsolved case, Hoskins and Schaub are driven to find justice for Sister Cathy, undeterred by their lack of detective experience. They started a Facebook group and began meticulously revisiting every scrap of records and leads in the case. And yes, this is the same unsolved murder that compelled Baltimore County police earlier this year to exhume the body of the Rev. A. Joseph Maskell, who had served as the high school’s chaplain in the late 1960s and early ’70s.


(Netflix)

Although police said Wednesday that DNA results from Maskell’s body do not link him to crime-scene evidence, Maskell was accused by several former students at Keough and elsewhere of sexual abuse. Although he died in 2001, the Archdiocese of Baltimore finally paid settlements to some of his alleged victims last year.

Hoskins and Schaub, who had no inkling that anything was ever amiss at their idyllic high school, serve as ready-made characters through which “Keepers” director Ryan White (“The Case Against 8”) can sort through a story that is painfully tangled up in broader, awful details of ritual rape and a coverup by both church officials and local police. “The Keepers” also offers a thorough contextual study of the fervent Catholicism that plays a substantial part in Baltimore’s history and identity.

Schaub describes herself as “the intellectual,” preferring to dig through records and hunt for documents, while Hoskins, she says, is “the bulldog,” willing to knock on doors and ask tough questions. “Whoever murdered [Sister Cathy] has gotten away with it,” Schaub says. “And she has never gotten justice.”

Blessedly short on theatrics, “The Keepers” skillfully walks viewers through the many details of the case while following Schaub and Hoffman’s progress. (If you’re a fan of how Marylanders pronounce their “o’s,” then you’ve come to the right seven-episode docu-series.)

Zeroing in on Maskell’s involvement (the working theory is that he got someone else to murder Sister Cathy because she was going to reveal the abuse of girls at Keough), “The Keepers” gets embroiled in a tragically familiar narrative in which victims came forward in the 1990s only to find themselves silenced by church authorities and statutes of limitation.

In addition to giving these victims enough time and empathy to tell the story that others refused to hear, “The Keepers” takes its own initiative to seek out some potential witnesses and documents on Schaub and Hoskins’s long to-do list. At occasional points, the series also looks at another unsolved murder of a young Catholic woman that happened around the same time.


The Rev. A. Joseph Maskell, left, the longtime suspect in the 1969 death of Sister Cathy Cesnik, and the Rev. Neil Magnus, who was director of religious services at Archbishop Keough High School in Baltimore. (Netflix)

Abbie Schaub and Gemma Hoskins in the Netflix documentary series “The Keepers.” (Netflix)

Like all serialized podcasts and documentaries, “The Keepers” sometimes grows redundant, partly in service to helping its audience keep the details straight and partly so it can float some rumors and theories without seeming irresponsible. Pacing is difficult in a project like this, but an urgent momentum takes over right where it’s most needed, creating the sense that a solution is within grasp.

Near the end, however, we begin to see some of the weaknesses of dragging the story out too far. At times “The Keepers” seems overly eager to turn its camera suspiciously on those who have already been as forthcoming as they can be — including Gerry Koob, a former priest who also taught at Keough.

Judging from letters and poems that went back and forth, Father Gerry and Sister Cathy came close to leaving their vocations and getting married. Koob’s alibi for the night Sister Cathy vanished (he was seeing “Easy Rider” at a theater with another priest) is at first presented as airtight; it’s never clear why “The Keepers” feels a need to circle back and probe it further, to such a degree that Koob’s present-day wife has to explain why she trusts that her husband is telling the truth.

The problem is that, by this point, obsession has set in for everyone involved, including the viewer, who now shares the frustration of dead ends. By the final moments, it’s impossible not to be outraged over missed opportunities and blind eyes that were turned. So, yes — dig up whomever and whatever still needs to be dug up; unseal whatever documents are still being hidden. Schaub and Hoskins are absolutely correct: Sister Cathy still needs and deserves our help.

The Keepers (seven episodes) begins streaming Friday on Netflix.