In a shadowy laboratory, Prof. Emmanuel Hildern (Peter MacQueen) eagerly divulges his revolutionary findings to a young doctor, admitting that he has unwittingly awakened an ancient evil far earlier than anticipated. As he narrates the events leading to this shocking discovery, it becomes apparent that his journey to New Guinea in 1894 was not solely focused on exploration but also driven by a deep desire for validation and recognition in his scientific community.
The flashback unfolds with Hildern’s jubilant return from his expedition, where he unearthed an unusually large humanoid skeleton, unlike any previously identified specimens. The skeleton’s sophisticated features and unexpected youth caused a whirlwind of emotions within Hildern — a blend of pride for his remarkable find accompanied by grief as he learns of his wife's death. This bittersweet moment is intensified when his half-brother James Hildern (David Horovitch), who managed the asylum where Hildern's wife was confined, informs him of his plans to publish a study on her mental health conditions while withholding support for future explorations.
As Hildern immersed himself deeper into his studies, his fixation on the skeleton grew, spurred by the mind-boggling idea that contact with water could cause the bones to rapidly develop flesh, reminiscent of age-old legends of malicious giants awakened by rain. With his theory taking form, Hildern determined that this skeleton was a remnant of such a nefarious creature, buried for centuries, now revealed as erosion exposed its resting site. By then, the local tribes would have attained the necessary knowledge to confront this terrifying evil.
Hildern's remarkable find ignited a fresh zeal in his research. He speculated that if evil could be treated as a living organism, it might be biologically contained and eradicated like a virus. Using cells from the flesh of the skeleton's finger, he created what he thought might be a serum to combat evil. In a nerve-wracking moment, he tested the serum on a monkey, observing impressive results that boosted his confidence in this inventive solution.
Meanwhile, as news of her mother's death reaches her, Penelope (Angie Joy), grappling with the painful truth she was kept from, is injected with Hildern's serum, aiming to suppress any signs of inherited insanity. However, this decision sets off a cascade of chaos, ensnaring Hildern in a series of unsettling events.
The next day, the formerly docile monkey from his lab has transformed wildly, using its new strength to escape and wreak havoc in the facility. In a surge of raw emotion, Penelope wanders off into the city, unleashing her pent-up feelings by assailing several men in a tavern and escalating her fury by fatally injuring someone in a nearby warehouse. The authorities swiftly respond to reports of the asylum's escaped patient, apprehending Penelope and returning her to her father's institution.
As the fallout from Penelope's violent outbursts becomes public, James grows increasingly worried about the fallout from his brother's experiments on their daughter. With his own research stalling and his hopes of earning the prestigious Richter Prize slipping away, he resorts to stealing Hildern’s findings, including the skeletal remains. Unwittingly, this choice propels a chain of events destined for calamity.
A careless accomplice inadvertently exposes the skeleton to the rain, triggering its imminent reanimation. When the carriage transporting the skeleton tips over, the revived corpse escapes, setting out on a vengeful path. Desperate to retrieve his misappropriated research, Hildern pursues the skeleton but is thwarted by a menacing figure lurking nearby. Upon his return home, he finds the resurrected entity has already begun to establish its evil influence, taking Hildern’s finger as a grim trophy while sparing his life, for the moment.
As Hildern concludes his cryptic tale, the focus shifts back to the laboratory seen earlier in the film. However, it becomes increasingly evident that this is not merely a place of research, but rather a confined space within an asylum — with Hildern himself trapped in a reality of his own making. The visiting physician engages James in a discussion that casts doubt on the legitimacy of Hildern’s claims of familial relations and whether Penelope, now a victim of madness, is truly his daughter. James, embodying the authority figure, observes that it’s typical for his patients to forge connections with him, given their fragile mental states and his role as their keeper.
Reflecting on how Hildern arrived at the institution around the time he was awarded the illustrious Richter Prize, James dismisses any familial links between them. As the camera focuses on Hildern’s cell, now morphed from a hub of scientific curiosity to a grim and unfeeling prison, Hildern's desperation mounts as his cries for help elude response.
The film ends with a chilling image of Hildern's left hand, its index finger absent — an unsettling reminder of the digit he had once removed from the skeleton in his "laboratory." Ultimately, it falls to the audience to piece together the tangled nuances of reality and illusion, as the dangerous intersections of truth and madness threaten to engulf them all.
