Few mysteries are as perplexing as serial murders. There’s a good reason. A serial killer is a different subclass of criminal. Unlike the garden-variety murderer, he rarely attacks people he knows. This makes it more difficult to identify or apprehend him. Potentially the culprit could be almost anyone, creating an unwieldy suspect pool. Think Jack the Ripper, or think the case about which I wrote my latest book, The Phantom Killer.

Having cut my literary teeth on the likes of Sherlock Holmes and Auguste Dupin, mysteries have always fascinated me. True ones especially, and the Phantom case lured me into the world of the serial killer. I wrote the book to correct the errors—some of them flagrant—that I saw in other accounts and dispel misinformation and rumors, as I’ve mentioned elsewhere, but serial killers had piqued my interest long before.

The Texarkana Phantom murders have baffled and fascinated lawmen and the public for nearly 70 years. Not very elementary, my dear Watson! “As a puzzle,” Dallas columnist Kent Biffle wrote a few years ago, “the case remains more popular than sudoku, but seemingly uncrackable.” He aptly described the status of the case, as a tantalizing puzzle.

Years ago I wrote a series of articles about the case. But I shied away from a book. It was exceedingly complicated, with sources lost or pilfered. Key individuals were dead, others hard to locate. It would take years. I shelved the idea. Then one day I realized I had to do it. An understanding of the nature of the serial killer would be integral. Eventually I was able to justify the book’s subtitle: Unlocking the Mystery of the Texarkana Serial Murders.

Though different killers may be driven by different motivations, they have at least two features in common. They basically attack strangers, and they repeat their crimes as if addicted. To make matters worse, a serial killer may change his m.o., his weapon, and even his motive. He’s hard to track down.

The serial killer intrigued me on several levels. On the surface, he may seem normal and law-abiding. His public persona helps him blend in. As one expert put it, he hides in plain sight. Without significant clues or eyewitness evidence, where do the police start? It’s a tall order.

His impact on the larger population adds to the tragedy. Once the media have branded him—in my book, newsmen called him the Phantom—he gains importance he has never known before. Playing an elusive cat-and-mouse game, he comes to believe he’s “brilliant.” He rarely is.

Whoever he is, wherever he operates, the serial killer generates as many questions as he has victims. Most of all, why does he almost always target innocent strangers? Why does he kill over and over? Why, why, why? The answers hold the keys to his antisocial behavior.

This history of this mystery became one of the most trying challenges I’ve encountered. No surprise. The mysterious criminal complicates everyone’s life in some way. Who wouldn’t be intrigued? Journalist James Presley lives in Texarkana, Tex., and has been nominated for the Pulitzer Prize. His new book, The Phantom Killer, will be published by Pegasus in November.