As Angus Flint, a dedicated Scottish archaeology student, digs deeper into the history of Mercy Farm, an ancient convent run by the mysterious Trent sisters, Mary and Eve, he uncovers a chilling relic: an unusual skull that appears to belong to a gigantic serpent, reminiscent of the local legend of the d'Ampton "worm." This mythical creature, said to have been slain by John d'Ampton, has haunted the tales of generations, echoing the whispers of a snake-like being that once roamed these lands.
The atmosphere intensifies when James d'Ampton, convinced that the existence of the d'Ampton worm is not mere folklore, finds an old pocket watch within Stonerich Cavern. This watch is linked to the Trent sisters' father, who vanished under mysterious circumstances near the opulent Temple House, owned by the enigmatic Lady Sylvia Marsh. Renowned for her ethereal beauty and mystical aura, Lady Sylvia conceals dark secrets associated with the ancient serpent god, Dionin. As she insidiously infiltrates Mercy Farm, her gaze gleams with otherworldly intent, leading her to steal the serpent skull and unleash a terrifying venom onto a nearby crucifix.
In a chilling turn of events, when Eve touches the cursed crucifix, she unwittingly absorbs the venom, awakening horrific visions that torment her—a crucified Jesus overshadowed by a monstrous serpent as horrific scenes unfold around nuns at the hands of Roman soldiers. Meanwhile, Lady Sylvia ensnares a young hitchhiker, using her captivating charm before delivering a lethal dose of snake venom, leading to a grim fate.
James, under the pretense of being a concerned friend, ventures to Temple House, where Lady Sylvia feigns a terror of snakes, her demeanor deceptively innocent. That night, James is plunged into a surreal nightmare aboard a plane, where he finds himself accompanied by Eve and Lady Sylvia, both masquerading as flight attendants, drawing him into a realm where the lines between reality and fantasy blur disturbingly.
With the dawn breaking over the rustic landscape, James, teamed with Angus, Eve, and Mary, embarks on an expedition into the twisting corridors of Stonerich Cavern. However, Eve’s ill-fated decision to retreat to Mercy Farm plunges her into danger as she vanishes, abducted by Lady Sylvia, who harbors sinister intentions. It becomes evident that a fearsome serpent lurks within the cavernous passages, a presence sensed by James.
As Angus and Mary infiltrate Temple House, they discover Eve’s mother, Dorothy, entranced and dangerously transformed into a feral creature. In a heart-stopping moment, Mary descends into madness, but Angus manages to extract venom from her neck just in time. With a mounting crisis at hand, James is driven to sever Dorothy in two, wielding a blade against the imminent threat.
The urgency reaches a peak as police officer Ernie arrives, responding to James’s frantic call. Under the guise of routine, Mary joins him on the journey to Temple House, only to discover that Ernie has fallen prey to the serpent’s curse. With quick thinking, Angus employs his bagpipes to lead Ernie away, ultimately bringing an end to the officer as Mary escapes into the underground tunnels.
Chaos ensues as Lady Sylvia captures Mary, preparing her as a sacrifice for Dionin in her lair deep within a pit. Yet, as darkness looms, Angus bravely intervenes, pushing Lady Sylvia into the abyss, where she faces her demise at the jaws of the ancient serpent god. Meanwhile, James ventures above ground to investigate the Stonerich Caverns, unaware of the perilous fate awaiting Eve beneath his very feet.
In a moment of great desperation, Angus seeks an antidote for Lady Sylvia's venomous bite, acquiring what he believes to be an antivenom serum from the local hospital. The sense of hope is shattered when a frantic call from a nurse reveals that the serum was actually arthritis medication, plunging Angus into disbelief. As the dread envelops him, he gazes into a mirror, wondering about the true consequences of this mistake.
Despite the grim news, Angus maintains a façade of cheerfulness during a celebratory lunch organized by James. However, as they arrive, his insincere smile gives way to a haunting reality when he catches a glimpse of his leg, revealing the ominous signs of Lady Sylvia’s bite, now an open wound pulsating with a life of its own.
