Just as there is no single form of poverty, there also is no distinct set of family patterns or life circumstances that leads to the choices these women made. No formula exists to explain what brought them to Gilgo Beach. Human trafficking was a factor for one of them, addiction for another.

But if they shared something, it was that they never fell off the grid or lived on the streets the way the TV procedural stereotype dictates. They all remained close to their families. They all came from towns with narrowing options and were seeking a way out. That’s one way of looking at “Lost Girls,” the title of my book about this case, later adapted into a movie: They were only “lost” insofar as we — the police, the media, the social safety net — elected to lose them, by deciding they were worth discarding.

Serial killers understand this, of course. Jack the Ripper targeted the women he did for presumably the same reason that the Green River Killer and Joel Rifkin said they did: These were women they believed no one would ever go looking for. And more often than not, sadly, they were right.

Now, 16 years after Ms. Brainard-Barnes went missing, we have an arrest, a suspect: Rex Heuermann was, it seems, living in plain sight, in a Long Island town a short drive from where the bodies were found. He has a spouse and children, and a job with a relatively high profile. In a place as densely populated as New York, he stands accused of a double life that seems hard to contemplate.

His advantage, it would seem, was that no one was looking for him, either. In cases involving escort work, the men who are customers often seem like footnotes, at least to the public. The police locked in on Mr. Heuermann only last year, more than a decade after the four bodies were found on Gilgo Beach.

For Ms. Cann and the other family members, that’s an eternity of wondering and waiting, and feeling every bit as discarded as the loved ones they lost.

Robert Kolker is the author of “Lost Girls: An Unsolved American Mystery,” the best-selling nonfiction account of the Gilgo Beach murders.