During a violent tornado that tears through the countryside, Janet Erin McGrane and her children Sally Sally Spurgeon, Jennifer Meg Saricks, and Alice Emily Boresow Maguire are on their way to the airport to pick up their military father, Lt. Maguire Aaron Laue. The family seeks shelter in a storm cellar beside a seemingly abandoned house, hoping the worst of the weather has passed. But once the storm subsides, a fallen tree traps them inside, turning a temporary refuge into a tense prison.
As fear mounts, Sally makes a bold but dangerous attempt to escape through a window, only to be bitten by something lurking outside and fall into temporary unconsciousness. Jennifer struggles to reach their father for help, but the phone lines—or the situation itself—offer no assistance, leaving the family with dwindling options and growing dread.
Their peril attracts the attention of Deputy Carr [Ben Jeffrey], who begins a determined search for the Maguire family. He enlists help from a neighbor, Mrs. Shurman [Joicie Appell], who claims ignorance about the Maguires and the surrounding mystery. Yet the truth unfolds with chilling clarity: the Shurman family appears to birth monsters whenever a storm rages, a discovery that deepens the sense of impending doom. The danger escalates when Deputy Carr is killed by an unseen monster—the kind that becomes clear only through the loss it leaves behind.
Desperation drives Janet and Jennifer to study the cellar further, and they uncover a hidden tunnel that leads to a moonshine distillery. In a tense moment, Janet and Jennifer venture into the distillery and seize a propane tank, hoping to use it as a weapon against what stalks them. While they are away, a monster breaches the cellar and abducts Alice, forcing the family to confront a much larger nightmare. Janet makes a final, self-sacrificing move to open the door by using the propane tank as a bomb, paying with her life for the chance to save the others.
The terror doesn’t end with their escape. Sally and Jennifer flee to a neighboring home only to discover that its occupants are transforming into monsters themselves. The attack sequence is brutal and relentless: Sally is assaulted by the transformed family, and Jennifer, isolated and outnumbered, is soon overwhelmed as more people around them change with the coming storm. By dawn, the area is quiet in a haunting silence, with no trace of Jennifer left—only the surviving family’s recent, sorrowful messages she had sent to her father throughout the night, a stark record of a night where a storm unveiled something monstrous lurking just beneath the surface.
