Season 1, Episode 1: Pilot - Widowed Sheriff Walt Longmire, urged by daughter Cady, returns to duty and seeks re-election against deputy Branch Connally. Investigating a young Mennonite woman's death, Walt uncovers her brother accidentally killed her trying to force her home. The episode concludes with the revelation of Branch's secret relationship with Cady, adding personal conflict to Walt's life.

Season 1, Episode 2: The Dark Road - Sheriff Walt Longmire investigates the death of Hannah, an exotic dancer with Mennonite roots, found on the outskirts of Absaroka County. The investigation reveals her brother, Samuel, accidentally killed her while attempting to persuade her to return to their community. Meanwhile, Walt deduces his daughter Cady has a secret boyfriend, who is revealed to be Branch Connally.

Season 1, Episode 3: A Damn Shame - A barn fire kills a man and two horses, initially appearing as a suicide. Sheriff Longmire uncovers that the deceased was not the owner, Ray Stewart, but a body used to fake Ray's death. Ray, a former mob accountant, faked his death for insurance and to escape the mob. A hitman tracks him, taking his family hostage. Ray sacrifices himself to create a diversion, and dies from a bullet wound, allowing Longmire to apprehend the hitman and save Ray's family.

Season 1, Episode 4: The Cancer - Walt investigates two murdered men, one a Cheyenne teen, uncovering a marijuana operation. He learns park ranger Eli killed a cartel member, Octavio, who shot the teen, staging the scene. Walt kills Octavio in self-defense, and Eli is arrested. The episode title subtly references the critical reveal that Walt's wife died of cancer.

Season 1, Episode 5: Dog Soldier - Walt investigates missing Cheyenne foster children, initially suspecting a sex offender. The "Dog Soldier" legend emerges. Walt uncovers a corrupt child welfare scheme by a social worker. Jacob Nighthorse is revealed as the "Dog Soldier," returning children to Henry Standing Bear, exposing exploitation.

Season 1, Episode 6: The Worst Kind of Hunter - Sheriff Walt Longmire investigates when a recently released convicted murderer is found mauled by a bear. The team, aided by Branch's eccentric former sheriff uncle, Lucian, discovers the bear was deliberately baited to attack. Walt ultimately confronts former prison warden Dan Blackburn, who confesses to orchestrating the murder. The episode concludes with Walt releasing the bear back into the wild.

Season 1, Episode 7: 8 Seconds - Walt investigates the brutal beating of beer distributor Chris Sublette and the theft of a seemingly worthless painting. The inquiry reveals that Chris was having an affair with another man, Dennis Nunn. Dennis's son, Zac, discovered the affair and, in a fit of rage, brutally attacked Chris, leaving him in a coma. Zac ultimately confesses to the assault, driven by his discovery of his father's secret.

Season 1, Episode 8: An Incredibly Beautiful Thing - Walt investigates the murder of a gas station owner who aided a distressed young woman. Henry's tracking uncovers an abandoned baby and a dangerous cult. The team rescues the woman, Evelyn, from the cult's influence. The episode concludes with the baby safely removed from the cult's reach, and the owner's sacrifice honored.

Season 1, Episode 9: Dogs, Horses, and Indians - Walt investigates the murder of the Tribal Council president, whose body was moved. The case uncovers the victim's ties to an underground poker game. Walt also discovers Cady and Branch's affair, a critical personal betrayal. The investigation is complicated by tribal politics, expanding the suspect pool.

Season 1, Episode 10: Unfinished Business - Walt investigates murders of teens acquitted of rape, revealing Rich, one of them, is the killer, coerced by Jake. Detective Fales informs Walt his wife's murderer was found dead. Cady learns her mother was murdered, not from cancer, causing a deep rift. Walt denies killing his wife's murderer, leaving the truth ambiguous.