In a valley high in the Sierra Nevada Mountains revered by the Paiute Indians as the Valley of Wonder, the natural splendor is protected by powerful supernatural forces, a power that is sometimes deadly. Valley residents enjoy unusually long and healthy lives and have developed a sacrificial ritual to slake the beast; the staking out of a bull calf at the rising of the full moon. When this ritual is interrupted, the leading citizen, Kidro Potter, is brutally slaughtered by the beast.
Kidro’s eight year old grandson, Jason Potter, and his widowed mother, Carolyn, struggle to survive in the city under the oppressive thumb of Carolyn’s divorced mother, Ellen Winslow.
Carolyn works at Kirby Publications where her boss, Tom Kirby, has personal motives for keeping her late on her son Jason’s birthday. When she is late picking Jason up from school, Jason and his best friend, Jimmy O’Conner, are attacked by gang members. Jimmy is killed and Jason is seriously injured.
Fleeing the dangers of urban life, Carolyn and Jason move to their inherited property, the ranch where her murdered husband grew up. Their house and others were built by long-time resident, Willis Donner, strong enough to withstand any external forces, provided the doors and shutters are properly barred.
After a ritual calf is slaughtered on Carolyn and Jason’s upper meadow, they decide to protect the calf offered for the following monthly ritual. That night, with their doors unbarred, the beast attempts to break into their home. Jason’s pit bull terrier chews off the front leg of the beast and they manage to bar the door. Carolyn wraps the amputated paw in a rug while it is still moving and puts it on the mantle, high enough to keep it from their dog.
The following day, Carolyn delivers the wrapped, amputated limb to the sheriff, demanding they stop staking out animals on their property, putting them at risk by attracting dangerous animals. The sheriff informs her that the village committee has an irrevocable trust deed to a small portion of their property, allowing them to use it as they see fit. When he unravels the amputated limb, it has become a human hand.
In an effort to maintain their safety, the sheriff takes the severed limb to the lair of the beast. That night, the beast returns and kills two of the valley’s residents.
Desperate for cash and wanting to marry into Carolyn’s newfound wealth, her publisher, Tom Kirby, visits for Christmas, promising to rid them of this problem. En-route, he purchases a rifle and silver bullets.
Christmas night, the full moon rises but the silver bullets don’t work and Tom Kirby is brutally killed.
Carolyn and Jason love their new home and decide to stay, leaving the ritual sacrifice to others.
The beast lives on, continuing to protect the Valley of Wonder.