Mark Baines and Jennifer Baines explore a grim Guanajuato mine where a satanic cult once built a temple and performed brutal rites, severing the left hands of their victims as offerings to the Devil. In the present day, the couple uncovers a small casket containing a severed hand and decide to take it back to their hotel room. That night, when Mark opens the container, he is violently seized and possessed by the monstrous hand, setting off a terrifying chain of events that pulls them into a nightmare they could never have imagined.
Their desperation drives them to Las Vegas, where the hand seems to unlock a dangerous luck for Mark as he wins a fortune at the gaming tables. Yet the possession gnaws at him from within, turning his fortune into a deadly curse as he tries to cut off the cursed limb. The botched attempt ends in tragedy when Mark is burned to death by his own hand, a macabre fate that also condemns his body to a burial in Los Angeles. Jennifer, shaken and alarmed, seeks help from Father Cunningham and warns that her husband might still be possessed, requesting an autopsy that could reveal the truth behind his death.
Before any examination can proceed, Mark’s horribly charred corpse inexplicably reanimates, bursting from the coffin and fleeing into the night. The nightmare accelerates when Sergeant Leo Matson arrives to investigate the strange events and is attacked by the undead Mark. In a brutal moment, Mark slams his left hand in a door, severing it from his own body; the hand then possesses the sergeant, pulling him into a new, violent obsession. Disturbed by his uncanny new appendage, Matson acts under its control, arresting Jennifer under false pretenses and heading toward a plastic surgeon’s office with sinister intent.
At gunpoint, Matson coerces Dr. Julian Rivkin into severing the hand, unleashing further horror when the severed hand shoots a nurse and brutally rips the sergeant’s face apart, killing him. The hand then possesses [Dr. Julian Rivkin], who is driven to cut his own hand off on train tracks, continuing the grisly chain of possession. The relentless force pursues Jennifer to a motel, but Father Cunningham intervenes, and together they manage to escape toward the church, convinced that the danger remains close behind them.
As the hand makes its way toward the church, it cuts the power and phone lines and stalks the fleeing duo. It succeeds in briefly possessing Father Cunningham, turning him against Jennifer with a knife. Yet Cunningham’s will proves strong enough to reclaim control, and he stabs his own hand to break the possession. Jennifer then helps him burn the severed hand with a blowtorch, scattering its ashes into the harbor in a final, symbolic attempt to end the menace.
Even after these desperate measures, the terror is not fully laid to rest. Back at a home of relative safety, Jennifer discovers that the hand somehow survived its cremation and returns to attack and kill her, leaving an ominous sense of dread that the darkness may not be easily quelled. The story follows a bleak, relentless march through possession and despair, where a single severed hand proves to be a conduit for an ancient evil that refuses to be laid to rest.
