Deputy Vic Moretti (Katee Sackhoff) and Sheriff Walt Longmire (Robert Taylor) race back to the Cowboy's Corner diner to find that the prisoner transfer has gone very wrong. The FBI agents are dead, and serial killer Wayne Durrel and the other prisoners have escaped and taken hostages with them.
Walt tells Vic that if he had been taken hostage, he would want to know someone was coming for him. She tries to stop him, but he's intent on going up the mountain after Wayne, despite the massive snowstorm that's on its way.
As soon as he hears what Walt has done, Henry (Lou Diamond Phillips) grabs two horses and races to find him. Branch (Bailey Chase) guesses what Henry's up to and convinces him to give him the second horse. Henry reluctantly agrees and they hit the trail.
Walt, newly outfitted with snowshoes and supplies from Omar's cabin, is following the Snowcat tracks when he notices an ammo clip in the snow. Agent Brooks, one of Wayne's hostages, is leaving him a trail to follow, while simultaneously relieving Wayne of precious ammunition.
Walt isn't the only one in tracking mode. As Branch and Henry make their way through the woods, Henry keeps an eye out for signs of Walt's passing. They're gaining on him, but still have a long way to go.
As Walt climbs, he begins to see things that aren't there. Detective Fales appears and interrogates him about his motives. Is he chasing a bad guy? Or is he running away from something? Walt looks again, and Fales is gone. He concentrates on climbing.
Walt crests a hill and spots the Snowcat barreling through the forest. Suddenly, he hears gunshots. He whips out binoculars and sees a prisoner on the ground in a pool of blood.
Walt steadies his rifle, but before he can return fire, a burst of bullets whizzes past him, and he tumbles down the mountain and into a freezing cold stream.
Walt manages to drag himself out of the deadly water before staggering to a nearby cabin. He makes a fire and spends the night warming himself. The next day, he continues his pursuit. He gets a signal on Vic's phone for a moment, but soon loses the call. At least Vic and Ferg know he's still alive.
Walt finally catches up to Wayne (Dan Hildebrand). After a brief gunfight, Walt manages to tackle the killer, and the two go tumbling to the ground.
Walt and Wayne are both exhausted from the journey up the mountain. They fight until they fall. Wayne tells Walt that the white buffalo they saw that morning was a sign to him that he would get away. Walt disagrees.
Walt struggles to his feet as he tells Wayne that the white buffalo calf was a sign for the Cheyenne, Arapaho, and Crow; the people that Wayne had been killing. It was a sign for a better future for them; a future that Wayne wasn't a part of. The men fight again, until they become too exhausted to carry on.
Walt leans up against a tree stump as Wayne falls to the ground. Walt sees a final apparition. Theo Halfmoon, Wayne's young victim, watches impassively as Walt reaches for his hat.
Walt slumps down against the stump and is still.
Henry and Branch finally catch up to Walt, and Henry immediately runs to his old friend.
Henry searches for signs of life as Branch inspects Wayne's lifeless, frozen corpse.
Henry grins as Walt answers his deputy, "Not yet."