The Sarge's American forces are stranded behind Nazi enemy lines. They come encounter an alien spaceship that has crash-landed in the woods as they make their way through the Italian countryside. Although the alien pilot is dead, one of the ship's passengers has escaped. As the GIs split off into smaller groups to track down the alien, they are pursued not only by the Nazis, but also by a slew of other aliens who have come to help their trapped party.