"Mercy Kill" (Touchstone, 320 pages, $15), Lori Armstrong's second mystery featuring ex-military sniper Mercy Gunderson, is set in western South Dakota, where rivers "gouge across the land," leaving mounds of "desiccated earth," and where the wind rages across the prairie as if it were its due. If this mystery's keen sense of place doesn't blow you away, its astute sense of character will.

The story is structured on issues of eminent domain. On the surface, it's about a proposed oil pipeline that would tear Eagle River County in two, with the complicating factor that the murdered Titan Oil representative is Mercy's former Army colleague. But it's beneath this surface that the real domain issues live, the ones rooted in Mercy's personal territory -- her head and her heart.

The army has "out-processed" Mercy, but she's not adapting well. How do you make peace with the outside world when you're still at war inside? Mercy is a Dakota cowgirl, belting out a Dixie Chicks tune with the same passion as she belts a bully in a bar with a pool cue. She prefers "solitude to socializing," but in this sequel, Armstrong peels away Mercy's personal armor, exposing her flaws with a raw, stinging honesty.

Mercy is "bleeding and howling inside," but outwardly she's "standing tall, strong, bulletproof." Not only is Mercy keeping her lover, her sister and her "wise old Indian" friend at a distance, but she's also making choices that continually sabotage her connections to them. She's stymied about whether to run her ranch or run away. Mercy's alienation is so acute that she torches an abandoned house, an act she deludes herself into thinking she's doing for altruistic reasons. By the middle of the novel, she is "drowning in the enormity of [her] mistakes."

Early in my career I taught in South Dakota and I've never forgotten that ripping wind, carrying pungent sage in the summer and biting cold in the winter. Toward the novel's end, standing on a plateau surveying her land and her life, Mercy centers herself in that wind. Her epiphany fuels the story's gripping conclusion, leaving me with hope that Mercy may have found a home at last.

Carole E. Barrowman teaches at Alverno College in Milwaukee. She names the top mysteries of 2010 at carolebarrowman.squarespace.com/carole/