While driving through the California desert, Roxy Miller nearly collides with a towering caveman named Eegah. She tells her boyfriend, Tom Nelson, and her father, Robert Miller, about the encounter. Intrigued, Robert, an enthusiastic author, sets out to find the creature, hoping it might be the subject of his next book. Against Robert's wishes, Tom and Roxy decide to follow him into the desert, equipped with little more than youthful determination and curiosity.

Their search leads them into the isolated canyon where Eegah lives. They discover that he has survived for millennia, cut off from civilization. Things take a dramatic turn when Roxy is captured by Eegah, who is fascinated by her beauty. Tom and Robert devise a plan to rescue her, leading to a series of tense confrontations and daring escapes in the desolate wilderness. The story combines elements of adventure, romance, and suspense, exploring human curiosity and survival instincts in an incredibly unusual situation.