Giant scorpions demolish Mexico City. They have been released from underground caverns by a series of volcanic eruptions, and it's up to Hank, an American geologist to stop them.
When the sheriff's son is placed on trial for murdering a stagecoach driver, the sheriff desperately searches for the real killer - and finds the trail leads back to his boy.
When electronics engineer Mitch MacAfee spots a UFO as "big as a battleship," from his plane, the Air Force scrambles planes to investigate. However, nothing shows up on radar, and one of the jets is lost during the action. MacAfee is regarded as a dangerous crackpot until other incidents and disappearances convince the authorities that the threat is real. Some believe it is a French-Canadian folk legend come to life, but it turns out to be an extraterrestrial giant bird composed of anti-matter whose disregard for human life and architecture threatens the world.
Private Meredith Bixby is so out of step in the Army that his six weeks of planned basic training has now stretched to 17 months. After he loses a tank, WAC Major Shelton, a psychologist, is assigned to make a good soldier out of him. She requests Corporal Dolan and Private Stan Wensalawsky to help with the training. Dolan and Stan both have scores to settle with Bixby and their "guidance" leads to more mishaps. Sergeant Pulley has them shipped out to Morocco.