Just as Thomas finished talking with the woman who was about to visit the Colonial Parkway, he turned to see another woman wearing a white tank dress that was printed with mug shots of various serial killers: Bundy, David Berkowitz, Aileen Wuornos. Thomas’s face immediately hardened. “I think there’s an obsession with the dark and our darkest impulses. People like to stand up and look over the edge of that precipice,” he said, speaking slowly as he searched for generous words. “But … I just throw my hands up in the air, like, why do you want to wear a dress with serial killers on it?” The woman had long since wandered off in the direction of the CrimeCon merchandise booth, with its “Basically a Detective” and “I’m Only Here for an Alibi” T-shirts.

For Thomas and other family members of murder victims, CrimeCon — now in its third year and hosting a sold-out crowd of 3,600 (up from 1,000 its first year) — represents a major and unprecedented opportunity. Twenty years ago, if victims’ family members wanted to draw media attention to a crime in hopes of shaking loose new leads and motivating law enforcement, there were just a few options — shows like “America’s Most Wanted” and NBC’s “Dateline.” Today, there are thousands. Entire networks — namely, Oxygen and a Discovery Channel offshoot called Investigation Discovery — are devoted to round-the-clock true-crime coverage. Writers like Ann Rule and Michelle McNamara have pioneered a “citizen sleuth” approach to crime, writing books that recount an active, often highly personal participation in the investigation of a murder. And then there’s the podcast universe, which after the massive success of “Serial” (“#FreeAdnan” T-shirts were everywhere at CrimeCon) has exploded with shows focused on true crime. The most popular — “My Favorite Murder,” a comedy-crime series, or “Crime Junkie” or “Up and Vanished” — are downloaded hundreds of thousands or even millions of times and frequently rank in Apple Podcasts’ top-25 chart.

When I spoke to Thomas before the conference, he said he had a singular goal in attending, as in everything he does related to Cathy’s case (including, he made clear many times, speaking to me): “I am trying to use media pressure to keep pushing the FBI to put resources into the Colonial Parkway Murders, a case that most experts tell me is a solvable case.” (The FBI has worked Cathy’s killing from the beginning because it occurred on National Park Service land.) Thomas feels that his only hope to keep the case alive after so many years is to drum up media attention. “I only have a limited number of cards I can play,” he told me.

Yet despite all the opportunities it offers, the true-crime boom — and CrimeCon itself — has put Thomas and other victims’ relatives in some awkward positions. There’s the very real risk of using these new outlets too aggressively and alienating law enforcement. And then there’s the fact that thrill-seeking true-crime fans (and the media serving them) can sometimes forget that Cathy Thomas and other victims were real people, not just characters in a titillating narrative. “Some people are approaching this as entertainment. Which is fine!” Thomas told me. “And then some of us are trying to use those avenues of news and entertainment with an objective towards solving unsolved cases. Occasionally, these worlds kind of collide.”

On the first day of CrimeCon, the massive line of ticket holders snaked through the first floor of the Hilton, past a jewelry shop and the elevators and almost all the way to the lobby. CrimeCon guests — like true-crime fans generally — are demographically similar to the victims most featured in true-crime shows and books: 80 percent female, according to organizers, and largely white. The CrimeCon line was dominated by white women: white women in large, laughing groups, white women tugging a husband or boyfriend by the hand, white women in “Stressed, Blessed and True Crime Obsessed” or “Talk Murder to Me” or “It’s Always the Husband” T-shirts.

I followed the line into the hotel’s convention space — a large ballroom and several smaller rooms — with Thomas and his friend and frequent collaborator Kristin Dilley, a true-crime writer who co-manages the Colonial Parkway Murders Facebook page. We navigated past a stall where people could pose for photos in orange jumpsuits and another allowing you to make jailbird “phone calls” to recorded voices from Oxygen shows — and then headed into Podcast Row. There, Thomas went into the mode he’d told me was his plan for CrimeCon: “trying to network my butt off.” He talked to numerous podcast hosts, some from shows he’s appeared on, others from ones he’d like to be on. He posed for photos that Dilley would later post to their Facebook page, grinning and stooping gamely over shorter people. “I have an agenda,” Thomas said as we strolled through the crowd. “If there’s an overlap of at least 60 or 70 percent of whatever someone else is trying to achieve and what we’re trying to achieve, I’m actually pretty comfortable with that.”

It wasn’t clear immediately that Thomas would become the public face of the eight families who lost people in the Colonial Parkway Murders. (One of the many unknowns about the case is whether the deaths are connected, but their similarities — four young couples killed or presumed killed near their cars in the same region of Virginia over three years — have caused family members and other observers to tag them collectively.) Cathy Thomas was a bold and brilliant Naval Academy grad, one of the first female surface warfare officers despite receiving more than her share of discrimination based on her gender and sexuality. She was killed a few weeks before Bill Thomas’s 30th birthday. Bill spent a few aimless, grief-dogged years spiraling through jobs and a brief marriage, before starting a public affairs job with the American Society of Composers, Authors and Publishers. He married again, had a son who is now 21, divorced again. In 2006 he moved to Los Angeles to do similar work at a higher level for the American Federation of Television and Radio Artists (AFTRA, now SAG-AFTRA after merging with the Screen Actors Guild).

One night in September 2009, a few weeks before the 23rd anniversary of Cathy’s death, Thomas decided somewhat at random to search on Google for information about his sister. From 7 until midnight, sitting in his office overlooking the Hollywood sign, he read every single article he could find about the killings. At some point he stumbled on a story about horrific crime-scene photos from his sister’s murder that had been released apparently accidentally. This appalled and infuriated him. It felt like an insult on top of injury after the long, slow process of the case. So, Thomas began advocating for his sister the way he had advocated for entertainment professionals most of his career: by getting loud. He secured interviews blasting the FBI’s treatment of the killings — and the bureau, he says, eventually promised him that it would put more resources into the investigation.

Still, a decade later, Cathy’s case, and all of the deaths and disappearances described as the Colonial Parkway Murders, remain unsolved. Thomas now treats the case like a full-time job, retiring from SAG-AFTRA last year and moving to the East Coast in part to focus more on Cathy. During treatments for oral cancer in 2014, he pulled back, but even then he “kept following up.” His friends and family worry about the amount of time he spends on it, he says. “People start throwing out words like ‘obsessed’ and ‘stuck,’ ” he told me with a laugh. Thomas himself worries about going too far. What keeps him up at night, he says, is anxiety over keeping a balance “between aggressive pursuit of moving the case forward and p—ing off our allies so they throw their hands up and aren’t willing to help us.”

It’s not clear Thomas could quit pursuing Cathy’s case even if he tried. He is less concerned about the “who” of the case and more about the “why”: What reason could there be for someone to kill Cathy? The unbearable wrongness of her death just cannot stand; it’s as if a terrible flaw has opened up in the universe. A jumpy, high-energy person with deep reserves of righteous fury, Thomas seems literally unable to rest until he finds the truth.

This restlessness could well be the engine that helps propel Cathy’s case to a close. But at times it has also seemed like a liability. As of CrimeCon, the FBI had not spoken to any of the families in over a year, Thomas says — because, he believes, agents don’t trust him. (Christina Pullen, a spokeswoman for the FBI’s Norfolk office, told me: “The FBI is actively engaged in this investigation and pursuing a number of new leads. We are making progress and want to ensure the momentum continues, so we are not able to share much information outside the investigative team at this time.”)

Restlessness has also driven Thomas into some decisions he remains conflicted over. In the early 2010s, Thomas and other Parkway families began approaching true-crime television shows. In 2013, producers of the now-defunct Investigation Discovery series “Dark Minds” agreed to film an episode on the Colonial Parkway Murders. Although Thomas was excited about getting Cathy’s story on Investigation Discovery (with its 82 million subscribers, mostly adult women), he squirmed watching. Like many ID shows, “Dark Minds” leaned heavily on reenactments, with actors playing the victims. “Those reenactments are just awful,” Thomas told me, describing them as cheesy and painfully gruesome.

More recently, Oxygen — a channel owned by NBCUniversal that relaunched in 2017 with a focus on true-crime dramas targeting women — has been developing a series on the Colonial Parkway Murders, hiring Thomas as a consulting producer. Again, he is enthusiastic about the project but concerned about losing control over Cathy’s story. “We understand that ID and Oxygen … need to tell a story. They provide something that can be very valuable for us as family members who are trying to increase visibility,” he says. “But there are times when I think to myself: How much more do I need to compromise to get Cathy and the other Colonial Parkway Murders victims’ stories out there?”

CrimeCon can occasionally feel like another compromise with the seamier side of true crime. There’s the “Dahmer & Bundy & Gacy & Berkowitz” T-shirts, the women wearing leggings or silk cravats or shirts with blood-spatter patterns. (Thomas cringed after seeing one of these: “I’ve seen pictures of blood-spattered T-shirts that I would prefer not to have seen.”)

And yet, CrimeCon provides a legitimate service for victims and their family members. Over the weekend, I spoke to a number of women who had come to New Orleans to do exactly what Thomas was trying to do: use the true-crime mediasphere either to advance their cases or prevent other crimes. Kathy Kleiner Rubin, attacked by Ted Bundy over 40 years ago, is writing a book about survival; she showed me her new large-format business cards, with her face and Bundy’s at opposite corners. Debra Newell — whose violent former husband John Meehan was the central figure of the Los Angeles Times series of articles and podcast “Dirty John,” as well as a Bravo TV show and Oxygen documentary — talked about the importance of educating women on the signs of psychopathy. Kelsi German, sister of Liberty German, killed along with her friend Abigail Williams in Delphi, Ind., in 2017, said she hoped the connections she made at CrimeCon would help keep Libby and Abby’s case in the news.

All of the women I met spoke enthusiastically about the value of having their stories amplified via true-crime media — a function that CrimeCon embraces. “It’s not about tabloid sensationalism,” Kevin Balfe, CrimeCon’s founder and executive producer, told me after the convention. “It’s about constant recognition that we are always dealing with the worst day of someone else’s life. How can we provide them healing? Or an outlet? Or, best case, the justice they seek and deserve?”

At times, however, this justice can feel selective. Thomas himself noted that Cathy, like the majority of true-­crime fans and on-screen victims, was white and female — whereas far more reported homicide victims are black and male. “There’s no question that victims who are female, white and middle class get significantly more play in the media than do people that don’t fit that profile,” he told me. “All you have to do is tune up and down the dial and watch these true-crime shows and look at who the victims are.”

Later on Friday afternoon, I met Amanda Shirley. I’d first noticed her earlier that day: a woman in an orange tank top standing just inside the CrimeCon entrance handing out orange rubber bracelets and a flier titled “Justice for DJ.” She had long brown-and-tan streaked hair and a sort of post-concussive softness that I learned to associate with family members of the slain and missing. When I found her that afternoon on Podcast Row, she told me her story, speaking in the abstracted way of someone who has narrated a traumatic tale thousands of times and accepts that she still must tell it many more.

In 2016, DJ Fickey, Shirley’s brother, died of a gunshot wound, and a medical examiner in Walker County, Ga., ruled his death a suicide. Shirley is sure that her brother did not kill himself but was killed. She has launched an impassioned campaign to persuade the Georgia Bureau of Investigation to reopen her brother’s case. But it’s been an uphill battle to attract media attention — in part, Shirley believes, because her brother was not a woman. “A woman’s body was found in this same county two weeks ago and people can’t stop talking about it,” she told me later. “They have talked more about her in the last two weeks than they have my brother in the last three years.”

The convention’s attendees are demographically similar to the victims most featured in true-crime shows and books: 80 percent female, according to organizers, and largely white — whereas far more reported homicide victims are black and male.

Shirley, in her tank top and streaked hair, looked uneasy among the professionally dressed and well-coifed podcast hosts staffing the booths. On one arm, she had a photo-realistic tattoo of her brother’s face, smiling peacefully. Her shirt was printed with an old photo of DJ hugging his three young kids. I asked how she was doing. “It’s hard,” she said, and started crying. “But as long as I’m being productive and keeping my mind off — it’s hard. How can you keep your mind off something when that’s what you’re doing?”

The next morning, Saturday, I met Bill Thomas for coffee and we returned to Podcast Row. Shirley was sitting outside, next to a giant plastic bin of rubber orange bracelets — she had ordered 3,000 for the weekend — wearing a new orange shirt. I stopped to say hi while Thomas went on ahead.

Shirley seemed more cheerful that day. “It’s going really good,” she said. “I’ve got probably 300 new followers on Twitter. … People want to help, they’re concerned, they care, and that’s hard to come by these days.” Nancy Grace had recognized her, she said, and they were talking about doing a podcast episode together. She seemed to be accomplishing what she had come for.

She mentioned that Thomas had been in touch over email, and I told her I was writing about him — would she like to meet him? Immediately she got to her feet. “It would kill me,” she said, to be 30 years in the future and not have answers in DJ’s case. “So, I want to hug him.”

We found Thomas on Podcast Row, schmoozing with a podcast host. Shirley gave him a big hug, and they went off into grim shoptalk. Shirley was visibly trembling as she described her family’s battles with the coroner, how the sheriff’s office wouldn’t even speak to them. “Boy, that sounds familiar,” Thomas said. “All you can do is stay with it.” His voice was calm, avuncular, the same tones he’d used to reassure the woman on Friday who was worried about camping on the parkway. He told Shirley to take care of herself, get some sleep, make sure she had a life outside of DJ’s case.

As she was saying goodbye, Shirley asked Thomas, “Does it get easier?” Thomas gave her a steady look and said: “It does. Passage of time, that’s the only thing I can say. It takes the edges off.” Shirley nodded, the corners of her mouth and her eyes drawn permanently down.

Kathy Kleiner Rubin, who survived an attack by Ted Bundy, seen in a photo in back, at CrimeCon.

Unlike Shirley, Thomas has decades of experience, professional as well as personal, in finding a way to tell stories people want to hear. He has frequently put those skills to use for other family members of victims, often reaching out as soon as a case hits the news. In many hours of conversation over the CrimeCon weekend, the only times I saw him get teary-eyed were when he was discussing women like Kelsi German and Amanda Shirley. But Thomas’s supernal ability to craft trauma into narrative doesn’t come without cost.

On Saturday afternoon, after hours spent wandering Podcast Row and a brief stop at a panel showcasing the “Dateline” hosts, Thomas and I stopped for coffee again and I brought up something I’d been wanting to ask all weekend. As a journalist, I’ve interviewed many family members of people who were killed. But I’ve never had as self-conscious and adept an interview subject as Thomas. At that point we had spoken for dozens of hours, both on the phone and as I trailed him through the conference. Much of our conversation was off the record (meaning I couldn’t use his quotes at all, even anonymously, in my story). Off-the-record Bill Thomas was funny, profane and crackling with what he called his “Irish temper.” On-the-record Bill Thomas was all of these things, but dialed down at least two notches, and with a close attention to driving home certain messages that he brought up again and again.

I don’t know this from personal experience, but I can guess that it is extremely difficult to stay on-message when talking about your sister and her girlfriend’s 33-year-old unsolved killing. So, on Saturday afternoon as we drank coffee in the Hilton lobby under a giant potted plant, I told Thomas that I’d noticed his tactics and that I was impressed. “It’s a good observation,” he said. “I’ve thought to myself that has to be the fourth or fifth time I’ve made that point in a 10-hour conversation. … I can’t say I didn’t give it the college try to work that into Britt’s story.”

Then he said, “You’re not unlike NBCUniversal.” He had just been discussing the upcoming Oxygen show, saying that although he knew he wouldn’t be fully satisfied with the result, he still felt it was worth it to keep the Colonial Parkway Murders in the public eye. Like Oxygen, he knew, The Washington Post Magazine was interested in Cathy’s story in part because our readers — like Oxygen’s viewers, like CrimeCon attendees — derive some complex pleasure from reading about serial killers. Thomas understood this and didn’t care, because of what he felt he could get from talking to me: “The Washington Post is the FBI’s hometown newspaper. Somebody in the FBI’s going to read this story.”

I’d been experiencing the conference as an outsider — not a victim or relative, not a member of the true­-crime universe with its occasional voyeurism and schlockiness, its moral gray areas. Now I realized I’d also been thinking about Cathy as a character — a character in the story I myself was writing.

Later, I asked Thomas what this was like, engaging with Cathy so often not as a living human being — the firecracker, the loyal friend, the sharp-as-nails young woman who told whiners to “suck it up, buttercup” — but as a character in true-crime narratives, like the Investigation Discovery show or this article. “It’s so sad that I end up talking about the painful last minute of Cathy’s life sometimes when it’s so much more fun to talk about all the rest of her 27 years with us on the planet,” he said. To a certain extent, he told me, he felt stuck in that final minute — using every tool at his disposal, his press experience, his Irish temper, to learn exactly what Cathy experienced on the night of Oct. 9, 1986. If Cathy knew, he speculated, she “would just be so p—ed at me.” “Maybe I, we, shouldn’t be kicking up such a fuss,” he said. “But I don’t know any other way to do this.”

A couple of weeks after CrimeCon, I called Thomas to check in. He was doing well, he said. He’d just heard from the FBI for the first time after the long freeze-out, and while he was hesitant to discuss what they said, he sounded pleased to be back in touch. Although he said the FBI clearly remained displeased with his media tactics, they had not entirely shut down the relationship.

That same week, I called Amanda Shirley. She told me she was happy about her CrimeCon experience. It had been enormously meaningful to connect with other people who’d lost family to violent crime. I asked if she’d gotten what she wanted out of CrimeCon in terms of propelling DJ’s story into the national media. “Yes,” she said. She laughed. “For one, there’s you.”

She still worried, though, about DJ’s case not providing a strong enough plotline to reach people and eventually bring about justice. Recently she filed a wrongful-death suit, hoping to use the court system to do what law enforcement wouldn’t: hold an alleged perpetrator responsible. On top of that, she believed that adding a new chapter would keep the public, and media outlets, interested in the case. “People want to see progress is being made,” she said. She sounded resigned to her role: keeping DJ alive not as a person anymore, but as a sort of narrative element. “If they don’t see progress,” she told me, “they just fall back off the story.”

Britt Peterson is a writer in Washington.