One on Top of the Other (Italian: Una sull'altra, which the English title translates accurately but without expressing twice the feminine),[3] also known as Perversion Story, is a 1969 giallo film directed by Lucio Fulci.

Written by Fulci and Roberto Gianviti, the film stars Jean Sorel, Marisa Mell, Elsa Martinelli, Alberto de Mendoza and John Ireland.

The first giallo directed by Fulci, its plot concerns George Dumurrier (Sorel), an unscrupulous San Franciscan doctor who is suspected of orchestrating the death of his asthmatic wife Susan (Mell) as part of an insurance scam, despite her seeming reemergence as Monica Weston, a high-class stripper.

George Dumurrier is a wealthy and self-centered San Francisco doctor who runs a clinic with his younger brother Henry, but leaves care of his asthma-stricken wife Susan to her sister Marta and a local nurse.

An insurance agent begins tailing George, discovers his affair with Jane, and brings his suspicions to a local police detective, Inspector Wald.

Meanwhile, an anonymous tip-off leads George and Jane to The Roaring Twenties, a strip club where they are both astonished at the appearance of Monica, a stripper who, although a blonde, bears an uncanny resemblance to Susan.

Some months later, on the eve of George's execution, Henry arrives for a visit where, in the privacy of an interrogation room, he reveals the truth: he and Susan hatched up this entire plot to get him out of the way and get the insurance money all for themselves.

At the last moment, a phone rings where the governor orders the execution halted as a telex arrives at the local FBI office that is forwarded to the prison authorities.

In a twist of fate, police in Paris have informed the US authorities that Susan and Henry have been shot dead in a local café by the spurned and jealous Benjamin.

This release, presented in an uncut 108 minute version with English and Italian audio tracks, was restored from the original negative (with additional scenes provided by a 35mm print).

[6] Writing for DVD Talk, Ian Jane rated the film four stars out of five, calling it "a well made thriller with some great twists, a strong plot and some fine performances".