In the town of Weaverton, signs of a circus are being posted. In the MacGruder's barn, a group of boys are holding a meeting about whether to admit two brothers, Tommy (Chance Michael Corbitt) and Ben (Ryan Todd) to their club, and are dared to climb Thunder Mountain, where it is said a giant lives. Tommy and Ben accept the dare and set out up the mountain. They are caught in a thunderstorm and take refuge inside the giant's oversized log cabin, and find mysterious carved wooden figures the giant has carved. Suddenly, the giant returns and finds the boys hiding under a table, but they escape with one of the wooden figures and go back to town. When the boys reach home they tell Zeke MacGruder their amazing story, but he doesn't believe them. The next morning, they set out with Zeke (Daniel Pipoly) to prove to him they have seen the giant. Tommy and Ben's younger sister, Amy (Noley Thornton) follows the three boys, and almost gets caught in a bear trap. The boys tell her to leave, but she persists and continues following them. The four children watch the giant from the woods moving logs by his cabin, and Zeke is scared and runs back home, but Amy steps out from the woods and introduces herself and her brothers to the giant, Eli Weaver (Richard Kiel). They help him with his chores including helping him plant young fir trees. The boys volunteer to get water for the trees and go in the cabin to fetch a bucket. When they do so, they discover some of Eli's gold nuggets. Tommy puts a few in his pocket, and they go outside and fill the bucket with water. Eli's pet wolf shows up to check out the children and after this, the children return to town. Amy discovers Tommy and Ben looking at the gold nuggets in their bedroom, and they allow her to have a nugget with the promise she won't tell their mother. Amy goes to the general store to buy candy with the nugget, and Hezekiah Crow (Jack Elam) overhears her and says he is an expert in gauging whether a nugget is gold or not, and proclaims the nugget as being "Fool's Gold". In trade, he offers her tickets to his carnival, and she bargains for extra tickets so she can invite Eli. She goes to see Eli and invites him to dinner and gives him one of the carnival tickets. Eli, now clean shaven, comes to the Wilson's house for dinner, and after dinner, repairs their cuckoo clock. Hezekiah Crow's circus parades through Weaverton, hosted by Zeke's father, Mr. MacGruder (Ed Williams). As Eli and Amy watch the carnival parade, which includes an elephant, jugglers, a lion, boa constrictor, clowns, a camel, and an acrobat. The final act, a trained black bear, reminds Eli of the horrible day a grizzly bear (Bart the Bear) killed his parents. At a circus booth, run by one of Hezekiah's sons, Percey Crow, (William Sanderson), Eli throws balls to knock down stacked pins to win a beautiful doll for Amy. Percey puts a rod through the pins so they can't be knocked over, but Eli's final throw breaks the pins and he expects the carnival man to give Amy the doll, but instead he gives her an inferior doll. Amy is disappointed, and Eli grabs hold of the carnival man and lifts him in the air and then drops him on the ground. Eli hands the beautiful ceramic doll to Amy. A crowd has gathered around Eli, and Amy's mother appears and scolds Amy for causing trouble. The crowd shout insults at Eli and Eli crushes the doll's head with one squeeze and warns the town to stay off Thunder Mountain. Amy tries to get Eli to stay, but he leaves for his cabin on Thunder Mountain. At a bar in town, several men (including old man Doc) are playing poker. Hezekiah and his two sons plot to go to Eli's cabin to obtain Eli's gold. Meanwhile, at his cabin, Eli burns the wooden statuette he carved of Amy. Amy goes to see Eli and says she is sorry for what happened in town, and the two are friends again. Eli and Amy go for a walk in the woods and he shows her the biggest tree in the forest "The General". Tommy and Ben go to find Amy and at the cabin are accosted by Hezekiah Crow and his two sons. They kidnap Ben, knock out Tommy, and take Eli's gold. Hearing the approach of a posse, they escape out a window in the back of the cabin, leaving Tommy lying unconscious on the floor. Meanwhile, in the woods, the grizzly (Bart the Bear) approaches Eli and Amy, and Eli fights the bear and knocks it out with a tree branch. Amy runs for the cabin and Eli limps along after her. Amy arrives at the cabin and runs to her mother. The posse do not ascertain what is going on and assume Eli has taken Amy's brothers and set out to catch him. While being stalked, Eli is shot and wounded in the leg by a man of the posse. Eli hides under a pile of leaves and surprises one of the men of the posse who has caught his leg in his own bear trap. He takes the man's gun and takes the trap off the man's leg. The posse burns Eli's cabin as revenge for their mistaken belief he kidnapped the children. Amy and her mom return to town with Tommy. The kidnappers go to the MacGruder's house to steal their belongings and Eli tracks them down and frees the MacGruder's and Ben. Hezekiah Crow tries to trick Eli and escapes out a window. Eli follows him and Hezekiah comes face to face in the dark with the true Giant of Thunder Mountain, the grizzly. Caught between Eli and the bear, he surrenders to Eli and the posse. The movie concludes with the town asking Eli if he would become their Sheriff, and promise to rebuild his cabin. Eli says he must return to the mountain, but leaves as their friend.