It mixes elements of Robert Louis Stevenson's 1886 novella Strange Case of Dr Jekyll and Mr Hyde with those of tales of Jack the Ripper.

Many years later, in late 1880s England, the adult Dr. Henry Jekyll is experimenting with the human psyche when he accidentally ingests a mix of ether and cocaine and goes insane.

One night, after he transforms, Jekyll is followed by Elisabeth to a brothel and then from there to a sadomasochistic threesome at a local abandoned warehouse where both of Hyde's partners go crazy and attempt to kill each other and her.

[3] Vincent Canby wrote in The New York Times that Anthony Perkins "gives a good, funny, if somewhat lopsided performance as the madman of medicine".

[1] TV Guide reviewed the film, giving it 1 out of 4 stars and saying, "EDGE OF SANITY obviously isn't meant to be taken seriously, despite its expensive production values and surrealistic photography—both surprisingly good.