When her plane develops engine trouble, Joi Landis parachutes into a rugged, inaccessible area of the American Northwest and is captured by a giant ape-like creature. Meanwhile, several weekend trail-bike riders stop for supplies at a general store owned by Mr. Bennett. After Rick and Chris separate from their friends Wheels and Peggy, they are attacked by a beast similar to the one encountered by Joi, and Chris is carried off. At the store, the sheriff is skeptical about Rick's story, but itinerant peddlers Jasper B. Hawks and Elmer Briggs, realizing the potential fortune to be made with a sideshow attraction featuring the beast, agree to help Rick search the dense forest. Captured by the beasts, the men learn from Joi of the legendary Bigfoot, a dying, sub-human race who have captured the women for mating purposes. Wheels arrives with other motorcyclists and Hardrock, a vengeful trapper. The creatures are dispersed, and all the captives except Joi are rescued. Saved by her Bigfoot captor from a mountain lion and a bear, Joi is taken to the beast's lair. She escapes when Hardrock wounds the Bigfoot; and the beast is sealed in a cave when one of the bikers dynamites the entrance. Having failed to secure a living specimen, Hawks hopes to persuade the women to relate their experiences as a traveling sideshow attraction.