Liz Flatt drove to Austin mostly out of desperation. She had tried talking with the police. She had tried working with a former F.B.I. profiler who ran a nonprofit dedicated to solving unsolved murders. She had been interviewed by journalists and at least one podcaster. She had been featured on a Netflix documentary series about a man who falsely confessed to hundreds of killings.

Although she didn’t know it at the time, Flatt was at a crossroads in what she had taken to calling her journey, a path embarked on after a prayer-born decision five years earlier to try and find who killed her sister, Deborah Sue Williamson, or Debbie, in 1975. It was now 2021. Flatt was middle-aged and coming out of one of the darkest moments of her life. Her mother had died, quite suddenly, two years earlier, and the grief from her death almost destroyed Flatt. Her father was gone, too — dead from a heart attack after years of fighting for the police to reinvestigate Debbie’s killing — and her older brother, Ricky, who was once a suspect in the murder, took his own life five years before that.

She had come to Austin for a conference, CrimeCon, which formed around the same time that Flatt began her quest, at a moment now seen as an inflection point in the long history of true crime, a genre as old as storytelling but one that adapts quickly to new technologies, from the printing press to social media. The gathering was smaller in 2021 because of the pandemic, but Nancy Grace, queen of true crime’s TV era, still showed up, as did Dr. Phil. On “Podcast Row,” Flatt wandered among booths for “Cults, Crimes & Cabernet” and “Murderish,” for “True Crime Garage” and “Die-alogue,” less a fan of the genre, which she never liked that much, than a scout on a search. She ran into a podcaster who covered Debbie’s story a couple of years before, a man who goes by the name Vincent Strange, and she commiserated with a woman whose mother’s murder also remained unsolved. Then, at another booth, Flatt met a woman who would later put her in touch with two investigators who presented at the conference that year: George Jared and Jennifer Bucholtz. They were podcasters, but Jared was also a journalist and Bucholtz an adjunct professor of forensics and criminal justice at the for-profit American Military University. Their presentation was on another cold case, the murder of Rebekah Gould in 2004, whose killer they claimed to have helped find using a technique that has quickly become a signature of the changing landscape of true crime: crowdsourcing.