The Potter family — Harry Potter Sr. and Anne Potter with teenage son Harry Potter Jr. and younger daughter Wendy Potter — moves into a new apartment complex in San Francisco, hoping for a fresh start. As they begin the quiet work of settling in, their world takes a strange and sudden turn. Wendy is attacked by a grotesque little creature wielding a glittering ring, and the creature quickly slips away, leaving Wendy shaken and confused. The same creature then captures Wendy and takes on her appearance, sowing confusion and fear within the family.
They soon notice Wendy’s unusual, increasingly aggressive behavior, but blame it on the stress of the move and the upheaval in their lives. Meanwhile, the troll—the creature behind the haunting disturbances—travels from apartment to apartment, transforming the living spaces into lush, otherworldly forests and spawning a procession of fairy-tale life, including goblins, nymphs, and elves, that weave a new, dangerous magic through the building.
Troubled by his sister’s sudden shift, Harry Potter Jr. seeks guidance from a mysterious older woman, Eunice St. Clair, who reveals herself to be a witch. She recounts a long, mythic history in which fairies and humans once shared the world, until a war reshaped the balance. A powerful wizard named Torok was in love with Eunice, and their union helped shape both realms; when Torok challenged the balance, he was transformed into a troll as punishment. Torok’s ultimate goal is to reclaim power, destroy humanity, and restore the fairy-tale world they once inhabited. He needs a princess to fulfill his vision, and he keeps Wendy alive to serve that purpose.
As Eunice and Harry Jr. uncover the extent of the magical invasion—the apartments themselves becoming gateways to a living fairy tale world—Eunice equips Harry Jr. with a magic spear, a weapon said to be capable of killing the largest and most vicious creature in this realm. But the struggle grows deadly: Eunice is attacked by Torok and is transformed into a tree stump, leaving Harry Jr. to confront the danger alone. He rescues Wendy from a glass coffin, though the spear is lost when Torok’s great batlike monster lunges at them.
In a climactic turn, Torok slays the monstrous creature to spare Wendy, effectively shattering the carefully built fairy realm. With the magical world dissolving around them, the family fights their way toward an escape just as the police arrive on the scene. Eunice is restored to her true self and parts ways with a final, bittersweet farewell. As the investigation unfolds, one officer approaches the lingering remnants of the alternate fairy world, and Torok’s dark ring is seen rising, hinting at the danger that still lingers.
