Teenage boy Zack lives on a farm in Tellico Plains, Tennessee with his mother Frances, younger sister Alice, stern and pious stepfather Nathan Crane and unpleasant, dim-witted stepbrother Cyrus. One night Frances sneaks out of the house while Nathan is asleep and begins having sex with Mike, a farm-hand who lives in a nearby shack. Suddenly a large meteorite crashes onto the property, emitting an eerie glow. Next morning, Alan Forbes, a physician who lives nearby, visits the crash-site, examining the meteorite which is a large sphere with a hard shell from which a noxious liquid oozes out. Before long, the object dissolves into glowing gelatinous liquid which seeps into the soil. Forbes wants to contact the authorities but is dissuaded by Charlie Davidson, local realtor and head of the chamber of commerce, who worries that the event will discourage the Tennessee Valley Authority (TVA) from building a new reservoir in the area. Forbes' bored wife Esther also manipulates her husband into keeping quiet, worried their house will lose its value.
The mysterious liquid soon begins to affect the farm. The water from the well grows cloudy and tastes unpleasant, fruit and vegetables grow invitingly large but are rotten and in-edible inside and the livestock begin to behave violently and show severe signs of infection. Alice is attacked and injured by infected chickens and Cyrus is nearly killed by a horse. Frances begins to have large boils growing on her face which soon grotesquely alter her features. She becomes mentally unstable, physically harming herself and attacking her own family. Believing the blight affecting his farm to be a punishment from God for his wife's infidelity, Nathan locks her in their bedroom, not allowing Zack to tell the doctor. Zack keeps himself and Alice free from the infection by consuming clean water and food he steals from Forbes' house.
Forbes secretly obtains a sample from the Crane's well and has it analysed at a nearby lab. The water is found to contain an strange, unknown element which is altering its metabolic properties. Carl Willis, a TVA representative who is surveying the local area for the planned reservoir, enters the Cranes' house looking for a glass of water. Helping himself from the kitchen faucet, he has just started drinking when he is attacked and nearly killed by Frances, who has gone insane and is horribly mutating. Worried that Forbes is going to alert the authorities, Davidson and Esther arrive at the Crane farm looking for the doctor but are attacked by infected dogs who have turned feral. Esther is mauled to death and Davidson hides himself in the cellar only to be killed by Frances who had been locked in there by Nathan.
By now Nathan and Cyrus are also infected and beginning to go insane. A guilt-ridden Forbes enters the house, hoping to rescue Zack and Alice but he is surprised and murdered by Nathan who then barricades the door. Cyrus attacks Alice but Zack fights him off, hiding his sister in a closet. Nathan corners Zack and is about to kill his stepson when he is stabbed by Willis who has just arrived. The ground begins to glow and heave beneath the house which starts to fall apart. Zack locates his mother just in time to see her mutated corpse dissolve into liquid. Willis gets Zack and Alice out of the house before it collapses and a dying Nathan and Cyrus are both killed by falling debris. Willis drives away from the farm, taking Zack & Alice with him.
In a postscript set some months after those events, a heavily bandaged Willis lies in a hospital bed, having become infected more slowly because he only drank a small amount of the farm's water. He is watching a news report on how authorities are promising that the blight from the farm will be eradicated. The final scene shows a location at night in the nearby countryside where ground and trees begin to heave and break apart, revealing more of the alien glowing liquid spreading onto the surface.Claude Akins as Nathan Crane
Cooper Huckabee as Dr. Allen Forbes
John Schneider as Carl Willis
Malcolm Danare as Cyrus Crane
Wil Wheaton as Zack Crane
Amy Wheaton as Alice Crane
Steve Carlisle as Charlie Davidson
Kathleen Jordon Gregory as Frances Crane
Hope North as Esther Forbes
Steve Davis as Mike
David Keith used his farm in Tellico Plains, Tennessee, for the exterior scenes. The interior scenes were shot in Rome.
MGM released the film onto DVD in 2007 as a double feature with its in-name-only sequel, Curse II: The Bite.
The Curse, along with its sequel was released on Blu-ray format from Shout Factory, under its sub label Scream Factory as a double feature on February 23, 2016
Lovecraft scholar Charles P. Mitchell referred to the film as faithful to the author's original work, but claimed that "[t]he last twenty minutes of the film are so disjointed that they virtually ruin the entire film."
In their book Lurker in the Lobby: The Guide to the Cinema of H. P. Lovecraft, Andrew Migliore and John Strysik write: "This third feature film treatment of [Lovecraft's] favorite story, "The Colour Out of Space", has it all... everything except good dialog, believable acting, and a cohesive plot."