Mitch MacAfee, while engaged in a radar test flight, spots an unidentified flying object. Jets are scrambled to pursue and identify the object but one goes missing. Officials are initially angry at MacAfee but areforced to take his story seriously after several other planes disappear. A gigantic bird, purported to come from an antimatter galaxy (and then later from the year 17,000,000 B.C.), is responsible for all the incidents. Mitch, along with his mathematician girlfriend Sally Caldwell, Dr. Karol Noymann and Gen. Considine and Gen. Van Buskirk, works feverishly to develop a way to defeat the seemingly invincible enemy. The climactic showdown takes place in New York City, with the bird attacking both the Empire State and United Nations buildings. It was defeated by a special type of isotope which was used to bring down its shield, allowing missiles to kill her as she crashed into the ocean outside New York City. The last scene shows the claw sinking to the bottom of the ocean.