“Wolves of Eden” is a remarkable mash-up of a novel. It’s both a western and a noir murder mystery. It is all the more remarkable since it is from the pen of Irish author Kevin McCarthy, whose two previous novels have been thrillers set against the background of the Irish Civil War.

What is equally noteworthy about “Wolves of Eden” is that it is structured as two compelling narratives moving toward the same climax, one narrative leading up to that climax, one narrative leading back to it.

It is 1866 in the American West of Red Cloud’s War, the conflict between the government of the United States and the Sioux and the Cheyenne. From a jail cell, Michael O’Driscoll keeps a journal of how he and his brother Tom have survived not only conflicts back in Ireland, but also fighting — ironically — for the North during the American Civil War.

Finding themselves no better off after that war than they were before it, the O’Driscoll brothers (that’s the name they’re using now) volunteer for the new combat in the American West. Tom has been damaged both physically and psychologically by a bullet to his face as he fought for the Union. All he can do now is lash out.

Michael has kept some of his humanity, however. It is he who recounts his life, his thoughts, via journal. It is a process he took up after overhearing Gen. William T. Sherman’s admonition to a group of officers’ wives that it would be “a crime on the historical record” not to keep an account of their adventures out West.

In giving an account of himself, Michael reveals his talent for a certain rough poetry in his worldview: “In truth I do think life is a series of things we do without thinking leading on & on until blood is spilt & when it spills everything seems such a surprise to us God Love Us All.”

The blood that Michael refers to in general becomes the specific reason Lt. Martin Molloy comes into contact with the O’Driscoll brothers.

Molloy is sent by the U.S. government to investigate the murders of the sutler (a civilian merchant who sells supplies at an Army post), his wife and an assistant at the isolated Fort Phil Kearny deep in Dakota Territory. Little does it matter that the sutler was ruthlessly dishonest and profited from an illegal brothel as well. Because of political interest, a murderer must be identified: “Boots on the gallows,” insists the government.

Solving the crime will mean a promotion for Molloy. Accompanying him are Rawson, an Army private; Jonathan, a Pawnee tracker; and Corp. Daniel Kohn, Molloy’s right-hand man.

Promoted to sergeant, Kohn initially takes on the investigation at the isolated fort to pass the time while Molloy recovers from a broken leg. What Kohn — who calls himself “a half-Polish, Silesian Dutchie Jew” — finds at the fort is a microcosm of the world of prejudice, fear and intolerance that both he and Michael O’Driscoll have separately experienced all their lives.

There’s a sense of other-worldliness surrounding the isolated Fort Phil Kearny. (Note the irony of the discriminatory fort being saddled with a decidedly Irish name.) The absolute brutality of the murders under investigation inside the fort and the abject violence of the hostility raging outside the fort collide in a ferociously lyrical finale.

Yet there remains a striking sense of humanity about “Wolves of Eden.” Whether in the world of solitary outsiders that Daniel Kohn uncovers or the one that Michael O’Driscoll endures, there are moments of dogged compassion. If that’s not enough to help us accept that “life is a series of things we do without thinking,” maybe Kevin McCarthy is reminding us that it’s nonetheless a kind of consolation along the way.

Steven Whitton is a retired Professor of English.