Cold Case of a Serial Killer's Daughter Solved in New True Crime Book
Investigator and podcaster Sheryl 'Mac' McCollum documents how she cracked one of Georgia's most disturbing cold cases — involving a serial killer's daughter and a misidentified skull
Sheryl 'Mac' McCollum, American criminal investigator and host of the podcast Zone 7, will publish Swans Don't Swim in a Sewer: Solving the Cold Case of the Flint River Killer's Daughter on May 12, 2026. The book is a documentary account of one of Georgia's most complex and disturbing cold cases — involving a serial killer's daughter whose fate went unresolved for years, and a skull that authorities had long misidentified.
A lifelong mission for one investigator
McCollum — known to most simply as 'Mac' — is not a typical true crime author. She is a trained criminal investigator who has spent decades working unsolved cases, both professionally and as a volunteer. Her podcast Zone 7 has built a dedicated following drawn to her methodical, evidence-based approach to cold cases: cases that have been shelved, forgotten, or mishandled by the system.
In her podcast episodes covering the Flint River Killer case, McCollum describes how critical errors in the initial investigation — including the misidentification of the skull — kept the victim's true identity hidden for years. It was precisely this kind of systemic failure that drove McCollum to dig deeper and ultimately crack the case.
For readers interested in true crime books, McCollum's work stands as a compelling example of how systematic, evidence-based investigation can bring resolution to cases officially considered unsolvable.
The Flint River Killer case — what we know
The case is set in the state of Georgia and centers on a serial killer whose own daughter became the victim in a case that went unanswered for many years. At its heart is a misidentified skull — one that was only correctly attributed after McCollum conducted her own review of the evidence.
Full names of the perpetrator and victim, as well as specific location details beyond the state of Georgia, have not been released ahead of the book's publication. However, McCollum has described in her podcast how DNA technology and a fresh forensic review played a decisive role in achieving the final identification.
Cases in which family members of serial killers become victims are rare, but they present unique challenges for investigators — not least because evidence may have been miscategorized from the outset, and because investigators at the time may not have been looking for a connection to an already-known perpetrator.
For those who follow American cold cases, the Flint River case is a striking example of why it matters to reopen old investigations with fresh eyes and modern technology.
Podcast and book as a combined investigation
McCollum has pursued a dual-format strategy in which her podcast Zone 7 serves as an audio documentary companion to the book. The podcast episodes on the Flint River Killer case go deep into investigative methodology, while the book brings the complete narrative together in one place.
This approach — combining podcast and book — has become increasingly common in the international true crime world, giving audiences the opportunity to engage with a case on multiple levels. It mirrors the model adopted by prominent true crime podcasters around the world, who have used the format to revive interest in cold cases and push for new investigations.
Why this case matters beyond the United States
Although the Flint River Killer case is an American story, it carries lessons that resonate far beyond Georgia. First, it illustrates how errors made early in an investigation can have consequences lasting decades. Second, McCollum's work demonstrates that private individuals with the right professional background can make decisive contributions to cases the official system has given up on.
Similar dynamics have played out in other countries, where new technology and determined independent investigators have brought crucial breakthroughs in seemingly hopeless cases. McCollum's book and podcast are more than entertainment — they make a powerful argument that cold cases deserve sustained attention, wherever in the world they occur.
