
Willis was the cinematographer of some of the most acclaimed films of the 1970s, among them The Godfather (and its sequel, The Godfather Part II), All the President's Men, Annie Hall and others. This would be his only attempt at directing a movie.

Emily Hollander (Shire) is the subject of a lesbian obsession of Andrea Glassen (Ashley), her next-door neighbor.

Emily, a shy, recently divorced woman, lives alone in a New York apartment. A man forces his way into her apartment and performs a bizarre "rape." He forces her to make sounds of erotic satisfaction, capturing them on his tape recorder. She reports the attack to the police, and while they are interviewing her, Andrea stops by to comfort her.

Emily seeks safety by moving to an apartment in another section of the city. However, while she is moving out, the same man tries to attack her again. This time Andrea conveniently passes by, and is able to prevent the man from entering Emily's apartment.

It becomes apparent that Andrea is not the helpful neighbor that she seems. For starters, she has the recording that was made during Emily's first attack. Andrea has developed an erotic fascination with Emily, apparently developed as she observed Emily through the apartment's windows. She hired a taxi driver to perform the attacks, with the purpose of gaining the recording, to which she repeatedly listens while fantasizing of Emily. Unaware of the situation, Emily continues to view Andrea as a friend. She also begins a relationship with the policeman (Cortese) who responded to her case. At this intrusion into her fantasy, Andrea becomes increasingly unhinged. She takes to spying on Emily through a telescope.

When Emily unwittingly hails a taxi driven by the very man who assaulted her, he strikes up a conversation "because you look familiar." She finally realizes who the man is and asks him to stop at a phone booth. She calls the police, who, amazingly, advise her to get back into the taxi and engage the man in harmless conversation until they can arrive to assist her.
With the taxi driver getting arrested and confessing to the entire plot, Emily and Andrea have a confrontation. Andrea professes her love for Emily, but Emily slaps her hard on the face and tells a devastated, weeping Andrea that they will never speak to each other again. Her ordeal over, Emily greets the detective at her front door.
Talia Shire as Emily Hollander
Joseph Cortese as Bob Luffrono
Elizabeth Ashley as Andrea Glassen
Kay Medford as Ida Marx
Michael Gorrin as Sam Marx
Russell Horton as Steven Hollander
Michael Lipton as Dr. Marin
Rick Petrucelli as Lawrence Obecny
Ron Ryan as Detective Swid
Linda Gillen as Police Woman
Tony DiBenedetto as Nick
Bryce Bond as Voice-over
Ken Chapin as Renting Agent
Marty Greene as Ira
Bill Handy as Desk Officer
Robert Hodge as Desk Sergeant
Kyle Scott Jackson as Detective
Pat McNamara as Doorman
Gerry Vichi as Ben
Ilana Rapp as Student (uncredited)
The film was the subject of many protests from gay rights activists who accused the film of being homophobic and resorting to hateful stereotypes of lesbians. David Denby attacked the film, saying "Windows exists only in the perverted fantasies of men who hate lesbians so much they will concoct any idiocy in order to slander them."
Gene Siskel and Roger Ebert selected the film as one of their "dogs of the year" in a 1980 episode of Sneak Previews.
Gordon Willis admitted the film had been a mistake, and later said of directing that he didn't really like it. "I've had a good relationship with actors," he reflected, "but I can do what I do and back off. I don't want that much romancing. I don't want them to call me up at two in the morning saying, 'I don't know who I am'".