Dr. Mercer Boley Dr. Mercer Boley and his daughter Diana Boley are traveling through Devil's Crossing, New Mexico, on a scientific expedition that promises new insights into ancient life. They stop at Uncle Willie's Desert Museum, where a tangle of bones is displayed: a large skeleton with wings and horns that seems almost too cohesive to be a random jumble of relics. Dr. Boley brushes off the display as a hoax built from unrelated bones, but Uncle Willie swears the pieces fit together, forming a single creature. While Uncle Willie spins tales of demons from American Indian folklore, an unseen force lashes out at the museum, triggering a fatal collapse and a fire that consumes the place. The father and daughter manage to escape with the horned skull, fleeing to a motel to study their find.
The morning after, they report to the police and return to the ruined museum site. There, they encounter a group of bikers—led by James Reeger—riding their motorcycles around the charred ruins. The police arrest the riders on suspicion of starting the blaze, despite the Boleys’ appeals for fair treatment. That night, two gargoyles slip into the motel room in search of the skull. They are smaller than the skeletal display and lack horns or wings, but their intent is clear. Dr. Boley gives chase to the road, where one gargoyle is struck down by a passing truck and dies, while the other escapes with the skull. The shaken Boley returns the body to the room, where the intoxicated hotelier, Mrs. Parks, complains of the disturbance even as Diana tries to reassure her that it was merely a family quarrel.
Diana goes back to the police station to plead for the bikers’ innocence, but the deputy tells her that only a judge can release them after charges have been filed. She shares with Reeger news about the dead gargoyle, though he dismisses it with a skeptical joke, suggesting that she and her father are “smoking” something. She does not reveal the possible supernatural angle to the police, perhaps because her father wants the evidence for study. She returns to the motel.
Two somewhat larger gargoyles return to recover the body, and the Boleys manage to slip away with it through a window, stashing the corpse in their station wagon. The gargoyles rip the passenger door off and then kidnap Diana, overturning the car in the process and leaving Dr. Boley unconscious. The abducted daughter is taken to a cavernous lair filled with eggs, where she meets the gargoyle leader—a larger being with wings and horns—who explains that these creatures have only lived for a few weeks after a 500-year incubation and that humans have tried to wipe them out repeatedly in the past, but this time they intend to endure. He also possesses several of Dr. Boley’s books, suggesting they were recovered from the car, and insists that Diana read to him. As she reads a passage describing a mythical encounter between a human female and a demon who molests her, the leader steps up from behind and reassures her that he has “no need for humans.”
Back at the town, Dr. Boley convinces the police chief to release the bikers and joins the search for Diana, with James Reeger accompanying him. Mrs. Parks and her helper drive off to summon aid, but their vehicle is later found abandoned and bloodied, and the helper’s body hangs upside down from a telephone pole with no sign of the attacker.
The gargoyle leader now has a queen, who also has wings and speaks. She warns that “men, horses, and dogs” are closing in on the cave and that many more eggs will hatch the next day. The leader orders that the humans must be stopped in the desert, and a brutal attack ensues. The chase spills into the open, with both sides taking losses.
The leader escorts Dr. Boley to the cave and declares, “this is the end of your age, the beginning of mine.” The queen, jealous of the leader’s attention to Diana, helps them escape. Reeger makes a last stand, dousing the eggs with gasoline and sacrificing himself to ignite a wall of flames that wipes out what appear to be the Gargoyle soldiers.
Seeing the tide turn, the leader realizes the war is lost. Dr. Boley finds a way to cripple the queen, striking her wing so she can no longer fly, forcing the leader to carry her away. They take off into the sky, leaving the desert to begin anew a hidden nest somewhere else.
