In 1925 Montana, the story unfolds around two wealthy ranch owner brothers, Phil and George Burbank. During a cattle drive, George encounters the widow and inn owner Rose Gordon, and his gentle demeanor quickly draws him towards her. In stark contrast, Phil, whose volatile nature is heavily influenced by his deceased mentor "Bronco" Henry, mercilessly ridicules Rose's son Peter for his lisp and perceived effeminacy. Not long after, George and Rose's romance blossoms into a marriage, and with George's financial support, Rose sends Peter to college to study medicine and surgery. She then takes up residence in the Burbank ranch house.
Phil's animosity towards Rose intensifies as he believes she has manipulated George for his wealth. His rough demeanor and constant jibes create an unsettling atmosphere for her. In an effort to unite their families, George hosts a dinner party, hoping to impress their guests, including their parents and the governor. However, a reluctant Rose is pressured into playing the piano despite her self-doubt. Amid the gathering, Phil's unkempt entrance and sarcastic comments only serve to deepen her humiliation. Following this incident, Rose, who used to shy away from alcohol, finds solace in drinking, deteriorating into alcoholism, which she keeps hidden from George.
As summer unfolds, Peter arrives at the ranch, where he becomes the target of Phil's taunts. Seeking refuge, he secludes himself, engrossed in dissection and studying diseases. In a hidden glade, Phil lies with Bronco Henry's handkerchief—a memento of complex emotions—until Peter stumbles upon Phil's personal collection of magazines featuring Bronco Henry. Watching Phil in a vulnerable moment heightens the tension between them. Surprisingly, Phil exhibits a gentler side, offering to teach Peter horse riding and lasso skills. As they bond, Phil's admiration for Peter’s keen observation skills grows.
During a fencing job, Peter encounters the carcass of a diseased cow, and with a scalpel, he explores the hidden threats of their environment. This chilling tale takes a sinister turn when Phil sustains an injury that becomes infected. Meanwhile, Rose's struggle with alcoholism spirals further as she struggles to cope with her reality, particularly the time Peter spends with Phil. In a bold act, she defies Phil's practice by giving unneeded hides to local Indigenous traders, an act that leads her to a drunken collapse, prompting George to care for her.
Despairing over the lack of hides to create Peter's lasso, Phil finds unexpected hope when Peter offers him the hide from the dead cattle. As they craft the lasso late into the night, the bond deepens with shared tales of survival, yet the undercurrents of regret and longing remain palpable. The next morning, chaos ensues when George discovers Phil sick in bed, his infected wound worsening. Before Phil can gift Peter the finished lasso, he’s rushed to the hospital.
A somber aftermath follows as George arranges a coffin for Phil, attending to his burial, while a doctor reveals the cause of Phil's demise—anthrax. This revelation leaves George perplexed, as Phil always took extensive precautions. Meanwhile, Peter, who refrains from attending the funeral, reads a passage from the Book of Common Prayer:
> "Deliver my soul from the sword; my darling from the power of the dog."
In a haunting conclusion, Peter places his completed lasso beneath his bed, wears gloves while doing so, and watches as George and a now sober Rose share a tender embrace, suggesting his calculated action to give Phil the diseased hide was a desperate bid to save Rose’s life.
