From her New York City high-rise office, a businesswoman screams in terror as something brutally decapitates the window cleaner working outside. Upon arriving at the office, Police Detective Shepard and Sergeant Powell struggle to explain how the man was killed. The next day, Powell investigates the murder of a man whose body was meticulously skinned. Meanwhile, former convict Jimmy Quinn begs a group of gangsters to allow him to work as a driver in their next heist. One afternoon, a rooftop sunbather is attacked and carried away by a flying creature, her blood dripping onto multiple pedestrians and causing panic in the streets below. Desperate for an honest job, Jimmy enters a bar where Shepard is having a drink, and asks to be their lounge pianist. The bartender dislikes his playing, however, and Jimmy has no choice but to help the gangsters rob a jewelry store. He calmly escapes on foot, but a truck strikes him and knocks his bag of money into the street. He limps to a payphone and telephones his lawyer to inform him that he is on his way to visit his offices for help. When he arrives at the offices in the Chrysler Building, however, the lawyer’s door is locked, and Jimmy sets off an alarm, attempting to break in. To evade a security guard, he climbs a series of staircases and ladders, which lead him inside the building’s spire. At the top, Jimmy discovers an enormous egg lying in a nest, before stumbling over a bloody human skeleton wearing a gold bracelet. Frightened, Jimmy sneaks downstairs and escapes the building. Meanwhile, the winged creature attacks more people and drops their body parts onto the street. Shepard speaks with a curator at the American Museum of Natural History, who tells him the about the human sacrifices made by the Aztecs to a winged serpent god called Quetzalcoatl. Believing many of the victims to be suicidal, Shepard borrows the curator’s books in hopes of learning more about the ancient rituals. Jimmy returns to his girl friend, Joan, and confesses about the failed theft and the dead body he discovered in the Chrysler Building. That night, a man in an Aztec mask and feathered costume slices open another man’s chest; the following morning, Shepard and Powell find the body along the Hudson River with the heart carefully removed. As rumors of a monstrous bird circulate the city, Shepard speaks with a Columbia University professor about the Aztecs’ sacrificial practices. One day, Jimmy is awakened in his apartment by two of the gangsters, Doyle and Webb, knocking on his door. Jimmy flees through the fire escape, but the men chase him through the streets and accuse him of keeping the jewelry store money for himself. Insisting that the loot is safely hidden, Jimmy leads them to the spire of the Chrylser Building. The gangsters knock the security guard unconscious and follow Jimmy to the serpent’s nest. Once the creature devours Doyle and Webb, Jimmy escapes, but runs into two policemen, who recognize him as the jewelry store robber and arrest him. At the police station, the commissioner informs Powell and Shepard that forty-three witnesses saw a flying creature snatch a man from his rooftop pool. Eavesdropping, Jimmy hears Shepard propose that the recent ritualistic murders are responsible for bringing the winged creature back to life. Later, Joan visits Jimmy in prison and urges him to reveal what he knows about the monster. Jimmy meets with the commissioner, Powell, and Shepard, telling them about the skeleton’s gold bracelet, which the police realize matches the description of an item worn by the missing sunbather. In exchange for revealing the location of the nest, Jimmy demands immunity for his crimes, $1 million, and rights to all photographs of the creature, but Powell and the commissioner refuse. Shepard brings Jimmy to a cafe and coerces him into telling him the location. Sometime later, Jimmy and Shepard lead a squad of policemen to the top of the Chrysler Building, where they shoot the egg. A baby emerges from the shell, but Shepard immediately kills it. Downstairs, Shepard refuses to award Jimmy his $1 million, claiming that the reward was for information leading to the fully-grown creature, not its offspring. Meanwhile, Powell and an undercover police officer watch two men meet outside the American Museum of Natural History and follow them to a warehouse. One man begins to perform the sacrificial ritual on the other, but Powell bursts in and chases after the killer. However, the winged serpent swoops toward the building, grabs Powell in its talons, and flies over the city. In Jimmy’s apartment, he and Joan break up after fighting about the $1 million reward. Police open gunfire as the serpent returns to its nest, but the creature grabs multiple officers in its mouth and flings them over the side, dropping Powell in the process. Riddled with bullets, the monster weakly flies away, eventually plummeting into the street below. Jimmy takes up residence in a hotel, where a man holds him at knifepoint and attempts to sacrifice him to the “plumed serpent,” but Jimmy refuses to recite the prayer necessary to complete the ritual. At that moment, Shepard arrives and shoots the man dead. As they leave the room, Jimmy vows to get a proper job before he reunites with Joan, who Shepard insists is waiting for him at the police station. In a desecrated building across town, another giant serpent egg begins to hatch.