Military forces have cordoned off a ghost town, aptly named Morgue, located in a remote section in the deserts of California while awaiting the arrival of a spacecraft from the planet Zanti. The perfectionist rulers of that planet, after making radio contact with our government, have decided that the Earth is the "perfect place" to exile their undesirables and criminals in exchange for sharing technological advances with Earth. They threaten total destruction if their penal ship is attacked, or if their privacy is not maintained. During the negotiations, Ben Garth, a bank robber on the run, along with his reluctant, morally deficient accomplice/girlfriend, Lisa, cross the cordon, and run down an armed sentry during the approach of the Zanti ship. After seeing the ship land, Ben climbs a small mesa to investigate the landing site. A Zanti regent emerges from an open hatch of the ship and kills Garth. The Zanti are revealed to be grotesque oversized ant-like beings with malicious human-like faces. The Zanti regent pursues Ben's now-terrified accomplice. Believing that their privacy was violated, the remaining Zanti prisoners commandeer the penal ship and land it atop the roof of the military command post. When the Zanti prisoners attack Earth's nervous soldiers, a brutal firefight ensues, and all of the aliens are massacred. The soldiers and airmen anxiously await the expected reprisal, but, instead, they receive a message of thanks from the Zanti leaders who explain that they were incapable of executing members of their own species so they sent them into the hands of a race who possessed no qualms about killing — the human race, referring to us as "practiced executioners".