Brigitte Fitzgerald Emily Perkins and Ginger Fitzgerald Katharine Isabelle vanish with their horse in the brutal wintry Canadian wilderness as the spring trading voyage to Hudson Bay sets out toward the fort. An elderly Cree seer woman warns that a terrible choice must be made to prevent one sister from killing the other: kill a boy, or doom both of them. As they ride away, unseen creatures close in, their howls ripping through the cold air, and the sisters’ horse bolts in panic. In the ensuing chaos, a Cree man—the Nathaniel Arcand who goes by The Hunter—intervenes, saving them and guiding them to Fort Bailey, a precarious refuge amid the snow and ever-present danger. Ginger explains to the fort’s wary residents that they are daughters of a drowned trader, seeking passage east.
The fort is beset by a hidden danger: the creatures are werewolves, and they have been a looming threat for some time. Murphy Matthew Walker, the fort’s physician, examines Brigitte’s wound and secretly applies a leech, seemingly to test for lycanthropy and to probe deeper into the sisters’ fate. The sisters are assigned a room once belonging to Wallace Rowlands Tom McCamus, the fort’s stern leader, where an eerie pulse of voices and hidden memories starts to surface. Ginger’s curiosity is drawn to a dimly lit, bolted room where a deformed boy is kept; the boy bites her shoulder as he bolts from sight, leaving a mark that will later complicate everything.
When the sisters attempt to leave, James J.R. Bourne, Wallace’s imposing sergeant, confronts them. A werewolf attack erupts, and a resident is killed. Reverend Gilbert Hugh Dillon grows suspicious of the sisters’ presence and leads them into an ostensibly safe building that unexpectedly houses a werewolf. The Hunter arrives in time to slay the creature, but Ginger’s nose begins to bleed—an early sign that she has contracted the infection. The strange, fated bond between Brigitte and Ginger tightens as they realize their fates may be bound to an ancient prophecy.
The truth about Geoffrey—Wallace’s son who lurks behind the fort’s quiet facade—comes to light when Ginger sleeps and the boy slips into her room. Geoffrey Stevie Mitchell bites Ginger, and Seamus Adrien Dorval investigates the disturbance, only to be killed in the confusion. Ginger is framed for Seamus’s murder, and Brigitte is taken captive by James while Ginger is led away for lycanthropy testing. Wallace arrives and counters James’s threats with his own force, offering a grim bargain: Brigitte’s sister must remain silent about Geoffrey’s actions, or Ginger will pay with her life.
In a grim turning of events, Ginger is strapped to an examination table while the doctor prepares to test her with a leech; Wallace shoots Murphy, and the men drift away, leaving Brigitte to face a harsh future. Ginger desperately seeks a way to stop what Geoffrey has started, and Wallace’s decision to end his son’s life compounds the pain. Ginger cannot bear to kill Geoffrey and implores him to stop; Wallace ends up killing his own son, ending Geoffrey’s danger in a brutal moment of grim resolve. Ginger and Brigitte realize their protection is crumbling, and the sisters decide to flee together.
Desperate for a cure, the sisters retreat to the Hunter’s cave, where the Cree seer and The Hunter explain that their coming has long been foretold and that the Red and the Black will decide the destiny of the werewolf bloodline. Brigitte enters a trance-like vision that seems to reveal her destiny—a moment in which The Hunter attempts to kill Ginger, but Brigitte, in a shocking turn, kills her sister instead. Brigitte emerges, discovering the seer dead, apparently slain by Ginger who has fled in the chaos. The Hunter then deceives Brigitte, guiding her back toward the fort with feigned help.
Back at Fort Bailey, Brigitte is taken prisoner as Reverend Gilbert tries to extract forgiveness to save her soul. When Brigitte refuses, Gilbert drags her onto the parade square and gestures toward a brutal burning. Wallace arrives and ends the threat with a decisive kill, and Ginger arrives moments later to turn the balance. Ginger lures James into a fight, slashes his throat, and opens the gates, unleashing the werewolves into the fort and letting them maul the remaining inhabitants. Wallace is bitten, sets the fort aflame, and then kills himself to prevent further carnage. The Hunter urges Brigitte to kill her sister, but Brigitte instead shoots him and escapes with Ginger, intent on survival and mutual protection.
With the prophecy broken, the sisters decide to run away together, bound by a shared vow to protect one another. In a final, defiant act of solidarity, Brigitte presses a cut on her hand against a cut on Ginger’s, their blood mingling as they both become infected, defying the forces that would separate them and choosing a perilous path forward, side by side.
