In the vast expanse of Wyoming, where hunting is a way of life, game warden Joe Pickett is used to catching poachers squatting beside the half-skinned carcasses of deer or elk. What he's not used to finding is an animal mutilated. But that's exactly what he discovers one early-September day in an empty meadow - a bull moose with its face sliced off.

So begins C.J. Box's fourth mystery featuring Pickett, an all-around decent guy, devoted husband to Marybeth and father to Sheridan and Lucy. He's a man who believes in the importance of his work, despite the long hours and low pay, but who often finds himself diverted from his regular duties and dragged into murder investigations that imperil the family he adores.

Box's novels take place in the rough-and-tumble cowboy world of the Bighorn Mountains. The books offer an unflinching look at the forces trying to diminish the environment (they deal with the fate of endangered species; the legacies of eco-terrorists, conservationists and forestry managers; the effects of drilling on the land). But they also present the portrait of a man who wants to believe the best about people, yet who learns, with sometimes disastrous consequences, that his trust can be misplaced.

In Open Season, the award-winning first book in the series, Pickett, as the new game warden, is nervous and unsure of himself. He describes himself as a man who has made a lot of "boneheaded" moves, including trying to arrest the governor for fishing without a license. He's a bad shot, and so clumsy that he actually loses his gun in a confrontation with a hunter. Most of all, he is naive, politically and personally. It takes a tragedy in his family to make him see people in a more cynical, hard-headed way.

At the same time that Pickett is learning ugly lessons about life on the job, he is also learning how blessed he is in his children. Author Box is the father of three girls, and perhaps that's why Pickett's sweet-natured relationship with Sheridan and Lucy is central in all the stories. Take for example Pickett's musings in Open Season:

The relationship between a father and his daughters, Joe had discovered, was a remarkably powerful thing. They looked to him to accomplish greatness; they expected it as a matter of course because he was their dad and therefore a great man. Someday, he knew, he would do something less than great and they would see it. It was inevitable.

In Trophy Hunt, Pickett's daughters are with him when he finds the dead moose. And they are with him when a horse is horribly attacked while still alive. In separate incidents, cattle are found mutilated, and two men are killed and cut to shreds. What is behind all of these gruesome deaths?

Pickett is asked to join a task force to find the culprits. The theories are all over the place. Pickett's part of Wyoming is undergoing a boom in drilling for natural gas, but the killings are spooking investors and undermining the price of land.

Could the deaths be linked to this new wave of investment? Or to the itinerant workers pouring in to the area?

Maybe it's aliens, more than one person suggests. As Pickett says, he's not much for that "woo-woo" stuff; he thinks the mutilations have a human origin. But the good citizens of Twelve Sleep County are plenty worried about creatures from outer space:

This thing is warping the mindset of the valley, Joe thought. Football practice was being held indoors. Out-of-state hunters had canceled $3,000 trips with local outfitters... . Livestock was being housed in barns and loafing sheds.

School children were wearing aluminum foil over their caps as they walked to school.

There are twists and turns that complicate the story's outcome. Just how does a wayward grizzly fit into the picture? And what does an alien-hunting outsider in an expensive Airstream trailer have to do with the case? What about the recurring dream 12-year-old Sheridan has about a coming battle between good and evil? The answers are never easy to predict; the book keeps the reader guessing until the end, and even then questions remain.

As mysteries go, Box's series is hard to label. Box is a little like Nevada Barr in his concerns for the environment and in his evocative descriptions of the land ("The sun was still two hours from dropping behind the mountains, but the sagebrush flats and red arroyos were beginning to light up. Pockets of cottonwoods and aspens pulsed with fall color.") He's certainly got a little of James Lee Burke's penchant for putting the family in harm's way.

But Box, who lives in Cheyenne, Wyo., is ultimately his own person. His style is down-to-earth and commercially appealing, sometimes hard-nosed and sometimes sentimental, with a Western locale that sets it apart. If his villains are occasionally too obvious (like the psychotic federal land manager in Winterkill who merely shrugs when her Yorkie is crushed by a Sno-Cat), Box more than makes up for it with his creation of the Pickett family, with all its domestic squabbles and loving reconciliations.

Box particularly has great respect for Joe Pickett. Over the several years in which the four books take place, Pickett learns to stand up to the corrupt sheriff and other politicians. And, as honorable as he is, he also learns to compromise his principles when necessary. Pickett is a man who can cry over his missing Lab, but can look the other way when someone avenges a horrific wrong to his wife and children. Yet, despite all he goes through, his core of decency remains untouched.

"I wish I were as tough as you are," Pickett says to his wife.

"You're better than tough, Joe," she replies. "You're good. I'll stick with good."
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Marietta Dunn is a former Inquirer editor.