Roberta is a bored suburban housewife who is fascinated with a woman, Susan, she only knows about by reading messages to and from her in the personals section of the newspaper. This fascination reaches a peak when an ad with the headline "Desperately Seeking Susan" proposes a rendezvous. Roberta goes too, and in a series of events involving amnesia and mistaken identity, steps into Susan's life.
An American professional gambler named Jack Weil decides to visit Havana, Cuba to gamble. On the boat to Havana, he meets Roberta Duran, the wife of a revolutionary, Arturo. Shortly after their arrival, Arturo is taken away by the secret police, and Roberta is captured and tortured. Jack frees her, but she continues to support the revolution.
A Reno singer witnesses a mob murder and the cops stash her in a nunnery to protect her from the mob's hitmen. The mother superior does not trust her, and takes steps to limit her influence on the other nuns. Eventually the singer rescues the failing choir and begins helping with community projects, which gets her an interview on TV—and identification by the mob.
Two homicide detectives are on a desperate hunt for a serial killer whose crimes are based on the "seven deadly sins" in this dark and haunting film that takes viewers from the tortured remains of one victim to the next. The seasoned Det. Sommerset researches each sin in an effort to get inside the killer's mind, while his novice partner, Mills, scoffs at his efforts to unravel the case.