Just after midnight, Old Porch, Egan, Kelly, and ranch hand Billings Gale give coordinated false statements to police, deliberately withholding contact information for Trent Riddle, who had witnessed Russel arrive home unharmed. Egan and Billings spend the night outside Riddle’s apartment hoping to silence him but find him absent. A flashback reveals that three years earlier Egan helped Old Porch murder a man who had tried to blackmail the family over a ski resort project. In return, Egan was entrusted with the family’s antique Colt revolver.

At 8:13 a.m., Old Porch sends Egan, Kelly, and Billings into Isatch Canyon on horseback, with informal clearance from Undersheriff Conrad Jewell, Porch’s brother-in-law. Two younger brothers, Sean and Shelly, secretly follow on dirt bikes.

Riding ahead, Landry finds the three Porch men blocking a flooded bridge. Egan accuses Kalin of murdering Russel and demands the return of the family’s Colt. Landry rides back up the canyon. From a high ledge, Kalin guides Landry and her horse up the treacherous Aster Scree to escape. After a tense standoff, Egan attempts the same ascent; his horse falls and is so badly injured that he shoots it. To frame Kalin for killing it, Egan shoots the dead horse a second time. With their escape route cut off and a storm worsening, Kalin and Landry begin a perilous high traverse across the canyon wall.

Late Wednesday night, Old Porch forces his way into Sondra Gatestone’s home, feigning a drunken apology to her while secretly gloating. Accompanied by Egan, Old Porch claims that Kalin kidnapped Landry and murdered Russel. Sondra, backed by her massive St. Bernard, Mungo, refuses to be intimidated and drives them off her porch with a garden hose. Inside the house, Allison has been hiding and listening to the conversation. Deeply unsettled by the Porches’ malice, the two mothers bond over tea and Sondra’s freshly baked cherry-rhubarb pies.

Allison opens up about her traumatic past with Kalin’s abusive father, Connor Mayhew, who is now incarcerated for life for killing a police officer. She reveals the true origin of the “curse” she placed on Kalin: When Kalin was 10, Connor discovered the boy possessed a supernatural talent with firearms, flawlessly shooting playing cards in half mid-air. Horrified by Connor’s plans to exploit the boy for money, as well as noticing how the gunfire caused nearby horses to permanently shun Kalin, Allison fabricated the curse, telling Kalin that if he ever touched a gun again, he would lose the horses he loved forever.

In turn, Sondra explains the bitter, generations-long feud between the Gatestones and the Porches, highlighting Old Porch’s ruthless, unending ambition to acquire land in the region. Connecting the dots of the evening’s confrontation, Sondra realizes that Old Porch intends to put Landry in grave danger and let Kalin take the blame. Recognizing the severe, escalating threat to both of their children, the two mothers agree they are now in a desperate fight to save them.

Driven by the plummeting temperatures and freezing rain, Kalin and Landry are forced to seek shelter. Kalin guides them to a massive, dark cavern he discovered during his summer rides with Tom, known as the Awides Mine. Upon arriving at the entrance, Tom’s ghost refuses to enter, claiming the mine is haunted and radiating a deep sense of dread. Knowing they cannot survive the storm outside, Kalin leaves his spectral friend at the entrance.

Inside a large, dry chamber, Kalin and Landry unsaddle the horses, tend to their needs, and build a warm fire. Using melted ice gathered by Landry, Kalin cooks a comfort meal of instant cocoa, ramen, potatoes, and mushroom soup. Landry helps dress Kalin’s severely rope-burned hands, and the two share stories to stave off the encroaching darkness. During their conversation, Landry finally reveals Egan’s claim that Kalin murdered Russel. Kalin is horrified but simultaneously relieved, as this horrific lie explains why the Porch brothers are hunting them.

Eventually, Tom and his spectral horse, Ash, cross the threshold and enter the mine. Tom draws his ghostly firebrand from its scabbard. Tom’s torch illuminates something terrifying hiding in the deepest shadows of the mine, a presence that only he and Kalin can perceive.

While Landry sleeps soundly, Kalin and Tom’s ghost witness a massive, spectral gathering within the mine. A ghostly Indigenous woman named Pia Isan approaches and demands that Kalin take her with them to the Crossing in exchange for the horses’ ultimate freedom. She warns that if they fail, Tom will be bound to her and the mine forever.

Soon, a chaotic parade of the dead floods the cavern, including Mormon pioneers, displaced Indigenous tribes, and Gatestone and Porch ancestors Alfred Gatestone and Wild Bill Hickman, who continue to argue over centuries-old grudges. An incomprehensible entity representing the Future then appears, cryptically warning the boys that if the morning sun touches the mine’s entrance before they depart, the mountain itself will oppose their journey.

Morning breaks, and the ghosts vanish. Landry wakes up, eats the last of their rations, and begins helping Kalin repack the horses. Playfully, she pulls out the Colt Peacemaker. Remembering his mother’s curse and the weapon’s dark history, Kalin reacts with absolute, visceral terror. He backs away frantically, refusing to touch it, and forces Landry to check the cylinder to ensure the hammer rests on an empty chamber before she stows it away. He then explains the curse his mother put on him.

When they finally step outside the mine to resume their journey, they see that the entire canyon is encased in ice. Kalin throws rocks to test the surface, watching them slide effortlessly over the cliffs, and realizes they are utterly trapped.

Desperate to locate their children, Allison and Sondra charter a small Beechcraft plane piloted by Tucker Wyatt to fly directly over the ice-covered Isatch Canyon. The turbulent flight is terrifying. They see no sign of Kalin, Landry, or the horses. Back on the ground, the mothers visit Chief of Police Beckham to assert Kalin’s innocence before securing the services of fierce, high-powered local attorney Holly Feltzman to protect their children from the Porches’ vendetta.

At the canyon entrance, an impatient Old Porch clashes with Undersheriff Jewell and Park Ranger Emily Brickey. Brickey reports that the trails are flooded and completely impassable. When Jewell insists on following due process for a safe “rescue,” Old Porch loses his temper with them. Jewell ultimately capitulates and allows Egan, Kelly, and Billings to enter the park on ATVs. Later, Old Porch receives a call from Senator Hays. Old Porch uses the fact of Russel’s death to garner sympathy and secure a fast-tracked floor vote for the federal land bill essential to his Four Summits ski resort project.

In Salt Lake City, Assistant Medical Examiner Dr. Annabelle Kasey performs Russel’s autopsy. She discovers a machine-cut shard of crystal lodged deep in Russel’s severed jugular. This physical evidence proves the murder weapon was a shattered drinking glass, fundamentally dismantling the Porch family’s claim that he was stabbed by a knife.

The morning sun thaws the ice, causing massive and deadly rockslides through the canyon. Kalin, Landry, Tom, and the horses carefully navigate the perilous, narrowing ledges. Along the way, Tom shares the tragic history of his ghost horse, Ash, who died of colic shortly after Tom’s father, Dallin Gatestone, died by a horse kick. The group eventually reaches the massive Ninth Scree, only to find the trail entirely washed out by the night’s violent storms, leaving a vast, unstable river of loose stone.

Kalin devises a desperate plan to cross by tying their lariats and reata together. Landry crosses first, skillfully navigating the shifting rocks to reach a dead ash tree on the far side. When Kalin attempts to send Mouse across on the tether, the scree gives way, dragging the horse and the dead tree downward toward the cliffs. Struggling against the tension, Kalin manages to cut the rope just in time. The untethered Landry miraculously guides Jojo and Mouse through the cascading rubble, lunging to the safety of the far side.

Before Kalin can cross with Navidad, the Porch brothers arrive at the base of the scree below. Egan spots Kalin through his rifle scope and immediately opens fire. Bullets strike the rocks, sending dangerous shrapnel flying. Unfazed by the gunfire and the collapsing mountain, Kalin mounts Navidad. With remarkable calm and equestrian skill, he fearlessly rides the horse across the collapsing scree, successfully reaching Landry and the other horses.