The film centers around the Merrye family, whose members are affected by the Merrye Syndrome, which causes them to regress into crazy and cannibalistic beings. Looking after them is family's chaffeur Bruno (Lon Chaney Jr.).
Problems arise as new legal guardians are given to the family, and their overnight stay turns out to be very troublesome.
Examples in this film:
- Black Dude Dies First: The postman is first one to go when he pokes his head through the house's window and Virginia kills him.
- Chekhov's Gun: The dynamite used for building the new highway.
- Daddy's Girl: Virginia, who gives her daddy a goodnight kiss even though he's nothing but a skeleton.
- "Do It Yourself" Theme Tune: Lon Chaney Jr. sings (or rather recites) the opening theme.
- The End... Or Is It?: The ending suggests that Peter's daughter Jessica might have the Merrye Syndrome.
- Eye Scream: Virginia stabs the postman in both eyes with her knives.
- Either/Or Title
- I am a Humanitarian: More regressed Merrye syndrome victims exhibit cannibalistic traits.
- Knife Nut: Virginia, who likes playing "spider" with two knives in hand.
- Lingerie Scene: Emily provides one, and Ralph peeps on her.
- Madwoman in the Attic: The Merrye children's uncle and aunts are kept in the basement of the house.
- "Not If They Enjoyed It" Rationalization: After being chased and raped by Ralph, Emily becomes so sexually insatiable she starts to chase him.
- Old Retainer: Bruno the family chauffeur acts as a surrogate father to Ralph, Elizabeth and Virginia.
- Psychopathic Manchild: Ralph. He is a full-grown man, but operates on the mental level of a very young child. Emily and Virginia also qualify to a lesser degree, being less regressed and in their teens.
- The Speechless: Ralph appears to be incapable of speech, communicating solely with animalistic grunts.
- Spiders Are Scary:
- The Merrye house is filled with spiders.
- Moreover, Virginia has two pet tarantulas named Winifred and Barney.