A newlywed deputy, Martin Gordon (Vic Savage), encounters an alien spacecraft that has crash landed in fictional Angel County in California. A large, hairy, slug-like, omnivorous monster emerges from the side of an impacted spaceship. A second one, still tethered inside, kills a forest ranger and the sheriff (Byrd Holland) when they independently enter the craft to investigate. The protagonists deduce that the monsters are mindless biological-sample eaters. The bio-analysis data is microwaved back to the probe's home planet through the spaceship.