With the help of local astronomer Dr. Stuart Kelston (Arthur Franz) and Dr. Blake, David soon realizes the flying saucer is likely the vanguard of an invasion from the planet Mars, now in close orbital proximity to Earth. Dr. Kelston contacts the U.S. Army and convinces them to immediately investigate: An important government rocket research plant is located nearby. In short order, the Pentagon assembles troops and tanks under the command of Colonel Fielding (Morris Ankrum). An alien sabotage plot at the plant is soon uncovered, leading back to the sandpit, and the army surrounds the saucer landing site.