In 1925 Montana, wealthy ranch owner brothers Phil Burbank and George Burbank encounter widow and innkeeper Rose Gordon during a cattle drive. The gentler George is infatuated with Rose right away, but Phil, influenced by his late mentor Bronco Henry, is more confrontational, cruelly mocking Rose's son Peter for his lisp and effeminate demeanor. As George and Rose marry, she utilizes George's financial support to send Peter to medical school while settling into the Burbank ranch house. Phil's disdain for Rose grows; he accuses her of exploiting George’s wealth, making her feel unwelcome with his rough demeanor.
George organizes an evening gathering with his family and the governor to introduce Rose and showcase her piano skills. Despite her reluctance and admitting her lack of talent, Rose is pressured into playing, ultimately embarrassing herself further when Phil, still dirty, interrupts with remarks on her practice. Upon leaving, she succumbs to her stress by drinking — a vice she previously rejected.
By the time Peter arrives for summer break, Rose's secret alcoholism deepens. Phil's relentless teasing drives Peter to isolate himself, preferring to study animals and diseases in his room. One day, while wandering through a secluded area, Peter discovers Phil with a handkerchief belonging to Bronco Henry. Peter stumbles upon magazines tied to Bronco Henry that depict nude men, further complicating his impression of Phil, who chases him away as he bathes in a pond.
Unexpectedly, Phil begins to show kindness toward Peter, teaching him horse riding and crafting lariats. This connection grows until they work together on a fencing task, during which Peter’s morbid curiosity leads him to dissect a diseased cow, while Phil suffers a wound. Peter confides to Phil about discovering his father hanged.
Rose, disturbed by Peter's bonding with Phil, spirals deeper into alcoholism. In a defiant act against Phil’s wasteful disregard for cattle hides, she gifts them to local Indigenous traders, which leads her to collapse from drinking. George cares for her, but with Peter offering the hide he cut from a carcass, both he and Phil bond over crafting a lasso in the barn. Phil reminisces about Bronco Henry's life-saving intervention during freezing temperatures, leaving unanswered Peter’s question about their nudity. The intimacy of their moment culminates in them sharing a cigarette.
Yet, the next morning unfolds grimly when George finds Phil bedridden with an infected hand. The delirious Phil desperately seeks Peter to deliver the lasso before George rushes him to the hospital. We later see George selecting a coffin, and during Phil’s funeral, a doctor informs him that Phil likely died from anthrax, leaving George bewildered since Phil prided himself on avoiding sick cattle.
Having skipped the funeral, Peter searches through a Book of Common Prayer, reading Psalm 22:20: > "Deliver my soul from the sword; my darling from the power of the dog." He then carefully places his finished lasso under his bed, watching as George embraces a now sober Rose, a sinister smile on his face. This suggests Peter had deliberately exposed Phil to the infected hide to protect his mother.
