The Brothers McKay is a novel in the Longmire mystery series, set in fictional Absaroka County, Wyoming.
Sheriff Walt Longmire and his undersheriff, Victoria "Vic" Moretti, learn that Pepper McKay, the widely despised patriarch of the O-Kay Ranch at the mouth of Crazy Woman Canyon, has been found dead in Crazy Woman Creek. Pepper married into the wealthy Harris family and transformed their cattle ranch into a high-end dude ranch. He has four sons: David, about 40, a former army and CIA operative from a previous marriage; Ian, late 30s, a journalist; Alan, early 30s, a novice at nearby Saint Benedict's Monastery; and possibly Manx Henenoka, a twentysomething head wrangler rumored to be Pepper's illegitimate son by a Shoshone cook. Manx was raised by Gary and Lynn Lyman, the ranch's longtime foreman and housekeeper.
At the ranch, Gary explains he found Pepper floating face down after a morning of fishing. Vic identifies a traumatic brain injury at the base of the skull. Manx, who shows no emotion over the death of the man rumored to be his father, leads Walt upstream to where moss has been scraped off a large rock and points out two sets of fishing-wader boot prints, suggesting someone else was present.
Lynn confirms Pepper was drunk that morning and describes decades of conflict with him. All three legitimate brothers were at the ranch the previous night for a family meeting. Alan spoke with Pepper that morning and found him depressed, while David's movements remain uncertain. Walt orders everyone to stay, but Manx defies him and drives toward Arizona before Highway Patrol intercepts him. Walt reveals to Vic that Pepper once tried to rape his wife, Martha, at a party years earlier.
Division of Criminal Investigation (DCI) forensic technician Tammy Payson identifies both sets of boot prints as the same brand and size Pepper wore. In the mudroom, Walt and Vic find a second pair of the boots, still wet, and notice a vintage Southern Cheyenne war club, a stone-headed weapon with beaded rawhide, resting in a mounted mule deer's antlers. David admits the wet boots are his: He went into the creek to coax his drunken father inside. He reveals that the family meeting concerned 63 million dollars Pepper had hidden in trusts while claiming poverty, and that both he and Pepper were romantically involved with Paetra Agirra, the niece of local mechanic Boris Agirra.
Meanwhile, Maxim Sidorov, a Russian ex-spy from a previous case, arrives penniless at the sheriff's office. He produces a photograph of Ruth One Heart, a missing law enforcement figure, at a Russian airport escorted by special forces operatives. Sidorov warns that the Regis family, whose son was killed in an earlier incident involving Walt, has outsourced their vendetta through Russian connections, keeping Ruth alive as bait.
The DCI autopsy confirms murder: subdural hemorrhage with retinal hemorrhages consistent with inflicted head trauma. Payson estimates the weapon was a baseball-sized rock. Walt notes that Pepper's flask was crushed against the front of his vest while the blow struck the back of his head, meaning he fell backward.
Walt interviews each brother individually. Alan admits he withheld information: His friend and fellow novice, Michael Rakin, was present the night before, along with Elder Zebrowski and abbot deputy Brian Schiffer from Saint Benedict's. Ian reveals that Paetra visited the lodge that night and that he himself previously dated her. David admits both Paetra and his ex-fiancée, Katherine Verkhov, were there; Paetra spent the night and he smuggled her out before dawn. Manx, working his mule Borax in the barn, warns Walt that all the brothers have lied. Vic discovers Paetra has a prior record for hitting someone in the head with a rock.
Walt returns to the ranch at 3 a.m. to retrieve the war club, but it has vanished. He finds Manx dead in his room, seated with his hands cuffed behind his back and a noose around his neck, staged to look like autoerotic asphyxia. Walt's dog, Dog, chases an unseen figure through the indoor arena, but the intruder escapes through a window. Henry Standing Bear, Walt's closest friend and a member of the Cheyenne Nation, determines the fleeing person was someone Dog knew or did not perceive as a threat. DCI confirms Manx was sedated before being killed. Vic drinks from Manx's travel mug and collapses from Rohypnol still in the tea.
Sidorov makes a critical connection. He asks whether Indigenous peoples used traditional weapons incorporating rocks, prompting Vic to recall the missing war club. He then declares that someone is committing crimes in imitation of Fyodor Dostoyevsky's
The Brothers Karamazov, with the McKay family paralleling the novel's Karamazov family. Katherine Verkhov confirms she was at the lodge that night and reveals that Alan wrote his doctoral dissertation on the novel. Walt finds handwritten letters from David to Katherine describing how he would kill Pepper by hitting him with a rock. David dismisses them as venting.
As the wildfire intensifies, Gary privately reveals that Pepper raped Lynn years ago, and their son Peter, who later drowned, was Pepper's biological child. Trooper Shane Wilson delivers the final evacuation order. During the departure, Walt discovers Paetra hiding upstairs, having secretly spent another night with David. He then finds Schiffer weeping beside the body of Elder Zebrowski, who shows signs of suffocation. Borax, Manx's mule, refuses to leave the barn and paws at a spot in a small corral. Walt digs there and unearths the missing war club, stained with what appears to be blood.
Rakin's abandoned car sits on the road into the canyon, his footprints heading toward the fire. Walt rides Borax into the burning canyon and finds Rakin about a mile in. They shelter in a rock overhang as fire closes from all sides. A stampeding elk herd thunders through; Rakin panics, runs, and is gored by a bull elk. Walt bandages the wound, then discovers Rakin's supposedly lost phone, a copy of
The Brothers Karamazov with the initials "MR," and Manx's missing Smith & Wesson .45. Rakin aims the pistol at Walt, but the safety is on. Walt tells him he knows Rakin did not kill anyone but is protecting someone. As fire engulfs the canyon, Rakin slips away.
Walt finds Rakin pinned under a burning tree with shattered legs. Using a rope harness, Borax rolls the trunk off him. Walt loads Rakin onto the mule and rides toward the exit, but converging fire fronts have nearly sealed the gap. J. R. Rose, the fire management commander monitoring the blaze, coordinates a precision water drop from a CL-415 water-bomber aircraft that opens a corridor. Borax gallops through moments before the gap closes.
At the undamaged lodge, Schiffer waits with Manx's .45. He confesses to killing Pepper, Manx, and Elder Zebrowski. What began as a literary exercise inspired by
The Brothers Karamazov, designed to torment Alan through the framework of his own dissertation, became a power grab for the position of abbot. When Schiffer orders Walt to surrender his weapon, Walt scratches under Borax's chin, triggering the mule's reflexive rear kick, which strikes Schiffer in the chest, splitting his sternum. Schiffer survives and is hospitalized under guard. Rakin faces charges as an accessory; his crushed legs mean he will likely never walk again. The novel ends with Sidorov revealing that the forces holding Ruth One Heart have offered to forgive all debts if Sidorov delivers Walt. Sidorov tells Walt they must prepare: "We are going to ends of earth" (349).