Nina Guerrera (whose name means “warrior girl”) escaped a serial killer’s clutches when she was a sixteen-year-old girl; now she’s an FBI agent hunting predators. Due to a name change after her emancipation from her abusive foster parents, Nina’s would-be murderer was unable to locate her again. Nina was “the one that got away”.

A viral video that shows Nina fighting off a rapist comes to the killer’s attention, and he sets out to finish what he started. But hunting Nina is not enough. The viral video gave Nina the attention he feels he deserves. Through a series of murders, he provokes the FBI into a public manhunt. Soon, he is “The Cipher”, a murderer who leaves behind cryptograms, much like the infamous Zodiac Killer.

The Cipher is a an FBI procedural by Isabella Maldonado, a retired police captain turned crime writer. To make it a story of our times, Maldonado has her killer use social media to turn his crimes into a spectacle. The FBI and the social media sites collaborate to keep the killer online, in hopes of tracking him down.

What if Zodiac Killer, but on Facebook?

This leads to wildly implausible plot developments, where “The Cipher” maintains a public leaderboard on his Facebook page, ranking the amateur investigators around the country who try to break his (often very simple) codes. Similarly, he is permitted to repeatedly post videos of horrific crimes to an audience of millions.

If you can believe that, you will probably not have an issue with the book’s more conventional tropes, such as the idea that an FBI agent would be allowed to lead an investigation while being very publicly threatened with rape and murder by its target, who previously raped and almost killed her.

Maldonado moves the plot forward at a steady clip, and The Cipher is certainly an easy read—I read most of the book on a transcontinental flight, and downloaded it for free through Amazon’s “First Reads” program. Maldonado deserves credit for writing in a very accessible manner, e.g., about investigatory procedures; she also sometime subtly repeats important plot points to help the reader along.

These are the kinds of writing techniques that make this book a page-turner. The positive reviews the book has received suggest that many readers found it thrilling. Maldonado has already written one additional novel featuring Guerrera, and there are plans for a Netflix adaptation of The Cipher.

For me, the many plausibility issues make it difficult to recommend the book, in spite of a likable heroine.