In 1958, the town of Centerville, Illinois, (filmed on location in Centreville, Illinois) was invaded by a race of aliens.

Neil Agar, a special agent with the State Department's Office of Security (the predecessor of the Diplomatic Security Service), is dispatched to Peckham, California to investigate the death of John Grubowsky, a bacteriologist working at the government-sponsored Brandt Research.

"Sister" Sarah Jane Butler, a hymn-humming religious fanatic who believes God has chosen her to cleanse the world of those who have sex for pleasure, seduces a bar patron, and guts him after the two leave together.

While searching for their estranged mother, two beautiful sisters, Dagmar and Ursula, arrive at a luxurious seaside hotel.

A shy and timid man who lives with his mother buys a plant he thinks talked to him. His loneliness is very apparent in the way he tries to turn the plant into a friend.

It is the last day on the job for hospital volunteer Sharon (Nancy Hoffman).

A race of extraterrestrial beings has evolved to the point that they only exist as beams of light.

NASA Captain Hickock arrives at Jackass Flats Proving Ground, a subterranean research facility. Mostly abandoned in 1962, it now houses “Project Shadowzone”.

The film opens with a green-skinned man (Franne Schacht) wandering aimlessly through the desert with a mysterious laser cannon attached to his arm.

Ann Collins, a painter, and her husband, David, are expecting a baby. What confuses the couple is that David has had a vasectomy, and Ann is not supposed to be pregnant.