Steven F. Havill, a resident of New Mexico, launched his Posadas County series in 1991 with his older undersheriff Bill Gastner as the protagonist in a vivid depiction of small town police work on the border of the United States and Mexico. Havill progressed the age of his characters more or less in real time; eventually Gastner retired and became a secondary character while his protégé Estelle Reyes-Guzman took over the lead in what has turned into an uncommonly good set of police procedurals.

Now in the 27th book Reyes-Guzman is a month away from retirement but she is as busy as ever. If It Isn’t One Thing, released today by Severn House, opens with a literal bang. A horrific collision at the intersection of two largely deserted state highways outside Posadas involving a pick-up truck hauling a valuable horse and a semi-trailer truck loaded with tons of firewood ended with the pick-up crushed underneath the semi. One driver is dead, the other too drunk to understand what has happened, the injured horse is wandering along the roadside, and wood is scattered in all directions.

Reyes-Guzman leaves the crash scene after a difficult all-night investigation only to be called to the site of a domestic violence incident where she arrives to hear shots and to see the deputy first on the scene down and bleeding. Both of the original participants are severely wounded, one fatally. Her immediate concern, after loading ambulances with the survivors, is to preserve the evidence to determine if the deputy fired the fatal shot and who initiated the gunfire.

When she starts checking on the owners of the vehicles and the drivers in the crash, she learns that the identification and the description of the dead pick-up driver do not match the person who left Portage, Nebraska, with the horse en route due west to an orthopedic veterinarian in Colorado Springs. The explanation of how and why the truck and horse changed hands and why they were in New Mexico has died with the driver. The owner of the horse burns up the phone lines between Nebraska and Posadas, demanding that Reyes-Guzman return the horse immediately and explain how a complete stranger took possession, neither of which she is able to do.

Interspersed with bits of information about the adult sons of Reyes-Guzman and their families and her plans for retirement, Reyes-Guzman investigates two knotty cases simultaneously, taking her once again across the border to Mexico to confer with the police there. Followers of the series will enjoy this new adventure. Readers unfamiliar with the Posadas County books can read this one as a stand-alone but they will miss some of the nuances.

Hints that Havill is going to stop spinning yarns about his fictional universe are obvious. I suppose it’s inevitable and I am glad that he has the opportunity to end the story line on his own, instead of a publisher deciding for him. However, the lively world of Posadas County has been a favorite destination of mine since I discovered it years ago and I will miss it. It has become a welcome escape from reality that I visit periodically; my deep gratitude to Havill for sharing his rich imagination with the rest of us.