One hour. Then it’s all tied up.

It happens every week: a mystery is solved, nice and neat, just as soon as your favorite TV detective has his “aha!” moment and before the last commercial has run. As the credits flash, you feel satisfied: You’ve just armchair-sleuthed an easy whodunit that practically explained itself. And, as in “Black Dahlia, Red Rose” by Piu Eatwell, it didn’t take 70-plus years.

Betty Bersinger only wanted her toddler daughter to get some fresh air.

But on that January morning in 1947, while walking past a vacant lot in their California subdivision, Betty noticed that something had been discarded, possibly a mannequin. She called the Los Angeles Police Department, who sent a squad car. Newspaper reporters, as they did those days, arrived at about the same time.

What they found shocked the community: the mannequin was human. A fresh corpse of a young woman, nude, mutilated, scrubbed clean, and cut in two. There was no ID near her body and few identifying marks but police took fingerprints and quickly learned that the dead woman was Elizabeth Short.

Born in a small town near Boston, Short was 22 when she was murdered. But though her death was tragic, it was almost no surprise. The beautiful middle daughter of five, often unemployed, she was a trouble-making, rudderless drifter who was known to enjoy the company of many men — some, married.

That, hints Eatwell, may have been Short’s undoing.

With the name of the deceased known, the LAPD began solving the crime with help from a department psychiatrist and, as tips poured in — including then-shocking suggestions that Short was a lesbian — they ultimately settled on not one, but three viable suspects to question. Unbelievably, just when it seemed like the “Black Dahlia Murder” was nearly tied up, everything fell apart: Scandal shook the LAPD and departmental changes affected the Dahlia investigation, which didn’t end so much as it fizzled out.

For 70 years, the question has lingered: Who killed Elizabeth Short?

Through old interviews, released documents, and good old-fashioned sleuthing, Eatwell thinks she knows.

It’s as good a hypothesis as any — and yet, it’s not easy getting there. “Black Dahlia, Red Rose,” starts out somewhat like an extremely gruesome vintage movie with hard-bitten, choppy sentences, bloody details and late-1940s slang that falls just short of noir and that, according to Eatwell’s end-notes, come directly from decades-old memoirs, written in that manner. That lends an authenticity that readers can appreciate, but it can be hard to follow. It lends a sense of time but, even with footnotes, expect occasional roughness in both style and story.

In the end, there were many years and many players in this tale, almost all of which are deceased, so Eatwell’s speculations are just that: speculation. Even so, determined readers will enjoy this book’s overall tone of fedora-wearing, hands-on murder-solving — and if that sounds appealing, stop here, start “Black Dahlia, Red Rose” and clear your calendar.

Your time will be all tied up.

The Bookworm is Terri Schlichenmeyer. Terri has been reading since she was 3 years old and she never goes anywhere without a book. She lives on a hill in Wisconsin with two dogs and 12,000 books.