[1][2] The story tells of vacationing American artist Jeff Farrell who becomes romantically involved with an older woman named Eve Beynat in southern France while at the same time harboring an attraction to her teenage stepdaughter, Annette.

Andy Black wrote: "Maniac was written and produced by Jimmy Sangster, with Michael Carreras handling direction, and what an under-rated director he was.

Donald Houston is George, an escapee from a French asylum (obviously Les Diaboliques had a big effect on Sangster, who also set Taste of Fear in France) who wants to kill his wife's lover.

"[6] Turner Classic Movies wrote "Maniac has excellent production values but labors under the weight of yet another gimmicky and obvious script by Jimmy Sangster...The acting is fine, especially that of Kerwin Mathews and Liliane Brousse.

";[7] and in The New York Times, Bosley Crowther wrote "Maniac has one thing and has it in spades—a plot of extraordinary cunning...(It) takes on a twitching suspense that simmers, sizzles and explodes in a neat backflip", though he concluded "Michael Carrera's direction is uneven and the characters are a generally flabby lot...Maniac remains a striking blueprint, with satanic tentacles, for a much better picture.