Jim Cole, [Clint Walker], his wife Angela, [Martha Hyer], their children Charlie Cole, [Kevin Brodie], and Gypsy Cole, [Victoria Paige Meyerink], along with their niece Meg, [Candy Moore], and their friend Sam Potts, [Don Haggerty], arrive in a small Wyoming town after Jim inherits a ranch and leaves his old life as a lawman behind. In town, banker Cotton Benson, [Regis Toomey], mentions a $675 mortgage on the property, and Jim hesitates to accept the land title because it would drain nearly all of their savings, but duty and hope finally push him to take the plunge.
Rancher Jed Curry, [Keenan Wynn], who once owned the land before losing it to Jim’s late uncle in a card game, makes it clear he wants the property back. The Coles move into a rundown cottage on the ranch, and as Jim begins to repair the fence, Jed presses him to sell—yet Jim stands firm, determined to make the place work. Back in town, Jim visits Wilhelmina Peterson, [Nancy Kulp], at the general store to learn about cattle deals. Wilhelmina sends Jim to Hazel Squires, [Ellen Corby], who insists she can sell cattle for a dollar apiece. When Hazel heads to check on the pigs, she discovers the animals are missing or dead—an ominous sign that Satan, a relentless grizzly bear, is raiding ranches and killing livestock. Many have tried to stop Satan, with little success, and the fear grips the countryside.
One brutal night Satan infiltrates the Cole place, killing Jim’s prize bull Duncan, spooking Sam’s mule, and injuring the family dog. The next morning, as the doctor stitches the dog, Jim and Meg head to the store for coffee, only to be met by harassment from Jed’s sons. A scuffle breaks out, but the Curry boys are soon dispatched, and Jed warns Benson to stay away from Jim’s land if he hopes to keep it safe for good.
With a need for stock after the attack, Jim secures a loan from Benson, offering collateral to cover the loan. He then travels to the Squires ranch to buy a replacement bull and cattle for breeding. Jed cautions Benson not to repeat the risky move and reminds him that he, as the bank’s major stockholder, has the power to influence decisions.
While they work, the mule returns only to perish, and Jim and Sam vow to kill Satan. They pursue the bear into the woods, but are forced to dive off a cliff into a lake to escape. Returning home from a dance, they discover Satan has decimated more cattle. Jim pleads for another loan, but Benson refuses, pushing the family toward desperate measures. Jed posts a $750 reward for anyone who can bring down the bear, drawing Cass Dowdy, [Leo Gordon], a bounty hunter with hunting dogs, into town. Jim had previously jailed Dowdy for murder, and Dowdy plans to hunt the bear not to protect the ranch, but to prevent Jim from collecting the reward and ruining his own finances.
Jim and Sam set traps for Satan, but the vigil fades as time runs short. Dowdy tries to sabotage one trap, only to be accidentally injured in the process. The two men confront each other again, and Jim defeats Dowdy, leaving him by the roadside. At home, Angela deals with the stress, while Charlie heads into the woods to spy on Satan alone. Jim follows and again encounters Dowdy, who narrowly escapes death. Satan attacks Charlie, who climbs a tree to survive, and Dowdy shoots at the bear to save the boy, paying with his life as he is fatally mauled. Jim fights Satan, injures the bear, and finally kills it. In the wake of Dowdy’s sacrifice, Jim consoles a dying Dowdy and, with Charlie safe, the family returns home to rebuild what was lost.
