Sheriff Walt Longmire and Dog are called on a routine search and rescue to Wyoming's Big­horn Mountains, where Walt finds himself on a rock outcropping remembering when his father told him about the first time he saw a man die. In the late forties, Bill Sutherland was shot but the investigation was stymied because no mem­ber of the elk camp--where he was found--was carrying the caliber rifle that killed the state accountant. When Dog discovers the miss­ing weapon, the sheriff of Absaroka County is plunged headfirst into a cold case. His inves­tigation quickly finds ties to a hidden mineral fund that someone is willing to kill to keep secret. The embodiment of the fair-minded detective, Walt is pushed to his ethical bound­aries. In his relentless pursuit of the truth, he discovers the rifle in question belonged to none other than Walt's infamous and uncompromis­ing grandfather, Lloyd Longmire.