The story begins in 1691 colonial America, specifically in Boston, Massachusetts. A sinister execution setup has been arranged, combining gallows and a pyre, while a distressed man is seen loading feral cats into a basket. Village elders enter a nearby prison tower adorned with a hex mark, where a man named Julian Sands is chained up. He faces execution for the crime of 'trafficking with the Devil' but refuses to confess. Amidst his chains, the warlock displays no remorse, leaving the elders to finalize their preparations for his demise.
Giles Redferne, played by Richard E. Grant, a self-satisfied witch hunter who aided in the warlock's capture, enters the cell to relish the warlock's impending fate, taunting him about whether Satan would intervene. The warlock cryptically suggests that Satan may yet save them both, leading to a violent confrontation where Giles declares he will watch the warlock die the next day. As he departs, he warns the jailer to keep the warlock shackled until his body turns to ash, but an unnatural storm suddenly envelops the village, emanating from the tower. Rushing back, Giles finds the warlock gone, having escaped into the storm with dark magic brewing around him.
Fast forward to modern-day Los Angeles, where a weather incident, dubbed 'The Devil's Wind,' leads to chaos as a blonde woman, Lori Singer, named Kassandra, awakens to find an unconscious man—the warlock—lying in her living room after a violent gust shatters her window. She and her housemate Chas (Kevin O'Brien) attempt to help him when all communications are cut off due to the storm.
As morning breaks, Kassandra navigates her daily challenges as a diabetic, balancing the demands of her life and work. She encounters the warlock, now awake, whose shock upon seeing a dated newspaper becomes a source of intrigue. Simultaneously, Chas finds himself in deadly peril when the warlock, intrigued by his Scorpio birth sign, violently attacks him, culminating in Chas's gruesome and untimely death.
Kassandra finds herself embroiled in a web of dark intrigue as a police detective investigates Chas's death. Meanwhile, the warlock seeks out a Channeler (Mary Woronov) to summon a spirit, but his malevolent demeanor exposes her as a fraud, resulting in her horrific demise.
Kassandra's attempts to enact normalcy collide with the supernatural when she experiences strange occurrences and witnesses the warlock's sinister power firsthand. A desperate attempt to flee leads her to confront Giles, who reveals their shared past linked through time and the warlock's ominous plans.
As they prepare to reclaim Kassandra’s stolen charm bracelet, which acts as the key to reversing the warlock's spells, they engage in a harrowing pursuit across California, fraught with peril, as the warlock attempts to complete his Grand Grimoire—the ultimate weapon that can unravel creation itself. With each confrontation, Kassandra ages more due to the spells cast upon her.
The showdown leads them to a remote cemetery where they unearth the past, literally, revealing a grim fate for Giles, while the warlock draws dangerously close to acquiring his power. As tensions mount, Kassandra confronts her fears and harnesses her resolve, leading to a climactic battle filled with desperate struggles for survival.
In a heart-pounding twist, Kassandra manages to thwart the warlock's plans at the last moment, sparking an epic showdown flooded with supernatural elements and timeless stakes. The story culminates as Kassandra chooses to bury the dangerous Grimoire deep in the salt flats, symbolizing closure and the end of dark magic's malevolent reach, all while marking a new beginning as she drives away triumphant yet forever changed.
