Crewman Thor shows his alien contempt for Earth's creatures by needlessly vaporizing a dog named Sparky with a disintegrator raygun.

Another crew member, named Derek, discovers an inscription on Sparky's dog tag and fears the Gargons might destroy Earth's native inhabitants.

Derek reveals an ancient book and turns out to be a member of an underground rebellion, which commemorates the more humane periods of their world's history, before they became mechanized slaves.

For the rest of the day, Betty and Derek have several run-ins with Thor, who vaporizes several humans (including Alice and Professor Simpson from earlier), and Joe follows up on stories of skeletons popping up all over town.

Shortly after, the Gargon grows immensely large after devouring a policeman investigating the alien's landing site and attacking numerous people.

The Gargon suddenly appears and ruins their romantic moment but Derek finds the raygun under a rock just in time for them to escape; unfortunately, it is damaged and out of power.

The giant Gargon begins heading towards the town so they follow and confront it, having used the electricity from the overhead power lines to fuel the raygun's components.

Derek then goes into the spacecraft alone and makes the ultimate sacrifice: leading the invasion fleet at full speed directly towards his ground location, which causes a massive explosion.

With a number of tell-tale landmarks like Bronson Canyon in Griffith Park and Hollywood High School,[5] which gives away the film's otherwise generic location.

[6] Producers Bryan and Ursula Pearson ("Thor" and "Hilda") and Gene Sterling ("The Leader") provided the film's $14,000 budget, which was less than shoestring even by the standards of the day.

According to Bryan Pearson, the crew employed many guerrilla tactics in order to cut costs: Director Tom Graeff secured, for free, the location used for Betty Morgan's house by posing as a UCLA student (which he had attended and graduated from 5 years earlier).

The use of stock footage in lieu of real special effects, and pre-Spielbergian "looking" shots[further explanation needed] that replaced actual visuals of the invading alien spaceships, seriously undercut the film's ending.

The same stock music has been recycled in countless B-movies, like Red Zone Cuba, The Killer Shrews and most notably Night of the Living Dead.

[10] The film failed to perform at the box office, placing further stress on an already-burdened Graeff, and in the fall of 1959, he suffered a breakdown, proclaiming himself as the second coming of Christ.

The film went on to become a cult classic among sci-fi fans and was later shown on Mystery Science Theater 3000 (as well as "riffed"), Elvira's Movie Macabre, and Off Beat Cinema.