In the Arctic, an earthquake breaks apart a glacier, and from within emerges a giant praying mantis, which takes to the air. It flies over a village of terrified Eskimos, attacks a remote radar outpost, and downs a military cargo transport plane before attacking an American military post. There, Colonel Parkman and his men attempt to stop the creature, but to no avail; it destroys the post and flies off into the night. The public is in a panic, while Congress remains skeptical that the thing exists. Parkman appears on TV to assure the public the menace is real, and that he has seen it and all the damage it has done. Civilians join the military in watching the skies. Finally, Air Defense radarmen are able to pick it up, as it reaches the United States and buzzes the Capitol and the Washington Monument. Ground forces attempt to shoot it down, without success, and the Air Force intervenes to engage it in flight. Finally, the mantis collides with a jet and, injured, falls to earth and takes refuge in a tunnel under the Hudson River. Parkman leads troops into the tunnel for the final battle with the deadly mantis.