Say it ain't so, Jo. Could this installment of William Kent Krueger's Cork O'Connor mysteries really be the end for the private investigator's down-to-earth helpmate? The two have had ups and downs ever since the series began with "Iron Lake." Typically, their arguments center on the dangers of chasing criminals, Cork's frequent occupation.

But this time, before they can reconcile over his latest decision to reapply to the sheriff's office, Jo's plane disappears in a mountainous area of Wyoming. Cork and their son, Stevie, join the exhaustive search, but weather conditions and the terrain conspire to keep the plane hidden. When Cork is nearly resigned to the idea that Jo's body will never be recovered, he hears that the elements may not have been the only factors in that conspiracy. The pilot's grieving wife shows up, asking the private investigator to clear her husband's name. She's convinced that he was not drunk and at fault, as witnesses stated.

With a surprising (and not wholly convincing) ally at his side, Cork uncovers evidence that might prove her claim -- and could even lead him to Jo. The tale is as gripping as any in the series, with twists as plentiful as the observations of American Indian life. As he does so well, Krueger sensitively lays bare the mistrust and deception that grow from isolation, poverty and discrimination.

But -- and I feel selfish and chauvinistic saying this -- I miss the give-and-take with Jo, and I wish Cork would stay in the Land of 10,000 Lakes, his typical stamping grounds. Krueger's descriptions of Wyoming are just as poetic ("There was nothing beyond the cottonwoods except the distant, inevitable collision of white earth and blue sky") as any he's written of Aurora, Minn. But the tensions between Cork's duty to his family and to his community have always been one reason I've thought his story was so special.

Still, change is inevitable, and it may just be time for Cork to widen his horizons. Fans, new and old, will be glad to see the re-release this summer -- by Atria Books, which also published "Red Knife" -- of the first seven books in this don't-miss series.

Kathe Connair is a features copy editor at the Star Tribune.