Years after bringing his beloved dog Sparky back to life, young inventor Victor Frankenstein has become something of a local legend in the quiet town of New Holland. Though life has mostly returned to normal, people still whisper about the strange storm that once awakened the dead. Victor, now a teenager with even greater scientific ambitions, spends most of his time working secretly in his attic laboratory alongside Sparky, whose stitched body still hides traces of unstable energy from the night he was resurrected.
As Halloween approaches, Victor begins detecting mysterious electrical surges beneath the old cemetery outside town. At the same time, several graves are found disturbed, and townspeople report seeing shadowy figures wandering through the fog at night. Victor initially believes grave robbers are responsible, but after discovering strange green lightning pulsing deep underground, he realizes something far more dangerous has awakened beneath New Holland.
Meanwhile, Elsa notices Sparky behaving strangely. The dog growls at empty corners, scratches frantically at basement walls, and disappears during thunderstorms. One night, Victor secretly follows Sparky into the cemetery and uncovers a hidden underground tunnel leading to an abandoned laboratory once owned by his late great-grandfather, Heinrich Frankenstein. Inside, Victor discovers forgotten journals describing experiments not only on animals, but also on ancient corpses buried beneath the town centuries ago.
Victor learns that Heinrich attempted to create immortal servants known as the Ghouls — reanimated beings powered by unstable electrical energy and controlled through fear. The experiments were abandoned after the creatures became violent and uncontrollable. Unfortunately, Victor’s original resurrection of Sparky unknowingly reactivated the buried energy network beneath the cemetery, slowly awakening the Ghouls from their underground tombs.
Soon, terrifying creatures begin emerging during violent thunderstorms. Unlike ordinary zombies, the Ghouls are fast, intelligent, and able to absorb electricity to regenerate their bodies. Led by a towering stitched monster called Morvane, they begin spreading chaos across New Holland, turning the town’s Halloween festival into a nightmare. While adults panic and attempt to flee, Victor feels responsible for unleashing the creatures and becomes determined to stop them himself.
Victor reunites with his old classmates, including Edgar and Toshiaki, who help him construct bizarre inventions to battle the undead army. Elsa also discovers that Sparky possesses a unique connection to the electrical force controlling the Ghouls. Although Sparky is frightened, he bravely leads the group through the storm-filled streets as New Holland descends into darkness. Along the way, Victor struggles with the same question that haunted him years earlier: just because science can bring something back, does it truly belong in the world of the living?
The final battle takes place at the towering windmill laboratory above the cemetery during a massive lightning storm. Morvane attempts to harness the storm’s energy to awaken thousands more buried creatures beneath the town. Victor and his friends fight desperately to stop him while Sparky sacrifices himself to overload the machine powering the Ghoul army. In an emotional moment, the laboratory explodes in brilliant green lightning, destroying the underground network and collapsing the cemetery tunnels forever.
In the aftermath, New Holland slowly rebuilds once more. Victor mourns Sparky deeply, believing he lost his best friend forever. But in the film’s final scene, as snow begins falling over the quiet town, Victor hears a familiar bark outside his house. He opens the door to discover Sparky sitting alive beneath a flickering streetlamp, his tail wagging gently as tiny sparks crackle through the night air.
