Lianna (Linda Griffiths) is the wife of a college professor teaching film and media at a university in a small to midsized town in New Jersey, and the mother of two children. In an attempt to give her husband more freedom, at his request, and cure her boredom in being a housewife, she takes a child psychology class with her friend Sandy.
Becoming more involved in the class and interacting with the female professor, she realizes she has a crush on the instructor, Ruth. Ruth invites Lianna over to her home for dinner and they talk into the night, Lianna explaining that she was a graduate student at one time who married the professor. They eventually sleep together and begin an affair, complicated by Lianna's husband's affair with one of his students. Lianna expresses interest in leaving her husband for Ruth, but Ruth backs away, warning Lianna that living with another woman would jeopardize her career as a child psychologist—and, to complicate matters, she has a partner in another city.
Lianna leaves her husband after a particularly ugly fight to live alone for the first time in years. Lianna visits a lesbian bar and attempts to connect with other lesbians through a string of affairs to explore her new identity. The film explores her loneliness, her changing relationships with her children, and her new relationship with Sandy, who is shocked at Lianna's revelations at first, but slowly begins to accept it and support Lianna.
By the end of the film, Ruth moves out of town (and out of Lianna's life) to California to take another teaching job. Despite now being alone in the world, Lianna and her friend Sandy reconcile in the final scene which mirrors the opening scene of Lianna and Sandy talking at a park playground.
The staff at Variety magazine gave the film a positive review and wrote, "John Sayles again uses a keen intelligence and finely tuned ear to tackle the nature of friendship and loving in Lianna." They especially praised the acting and the supporting characters' reactions to Lianna's lesbian affair.
In his New York Times review, Vincent Canby wrote, "Though Mr. Sayles's methods are antidramatic, the film is full of the kind of middle-class desperation that seldom finds its way into movies, where emotions are usually bigger than life. Lianna is never dull but it is so finely tuned that one has to pay attention to receive it properly. It doesn't knock you off your feet, slam you against the wall or leave you gasping for breath. It's civilized."
In a joint review of Lianna and another John Sayles film, Baby It's You, Rolling Stone's Michael Sragow commented that Sayles has his strengths but is considerably overrated, and compared both films unfavorably to his earlier Return of the Secaucus 7. He elaborated that Lianna is too ideologically single-minded while failing to offer any new insight or perspective on the subject of lesbianism. He also criticized the "truly embarrassing audiovisual montages", citing as an example the lesbian love scene being accompanied by the sounds of the women whispering in French.
Reviewing Lianna's release on DVD, film critic Glenn Erickson called it "daring" and "sophisticated". He found the film's strongest point to be that rather than becoming a "melodrama" of scandal, it focuses on the protagonist's isolation and self-discovery. By his analysis, the film "sidesteps position statements and stresses intimate character touches. Lianna doesn't ask us to condemn or condone anything, but simply to be understanding and sympathetic with each other."
Critics Frederic and Mary Ann Brussat wrote, "The screenplay by John Sayles is both congenial and wise... Viewers are sure to find much to savor in the moral and emotional confrontations. Lianna muses upon love, friendship, and camaraderie in a fresh but unspectacular way. It is an appealing movie worth experiencing."
The film is recognized by American Film Institute in these lists:2002: AFI's 100 Years...100 Passions – Nominated