A repressed spinster is transformed by psychiatry and her love for a married man.

Dowdy, thirtyish Charlotte Vale lives with her dictatorial, aristocratic mother in a Boston mansion. Fearing that Charlotte is on the verge of a nervous breakdown, her sister-in-law Lisa brings psychiatrist Dr. Jaquith to the Vale home to examine her unobtrusively. Jaquith's observations and conversation with Charlotte convince him that she is, in fact, very ill, and he recommends that she visit his sanitarium, Cascade. Away from her domineering mother, Charlotte recovers quickly, but does not feel ready to return home and accepts Lisa's proposal of a long cruise as an alternative. On board the ship, a newly chic Charlotte is introduced to Jerry Durrance, who is also traveling alone. The two spend a day sight-seeing together, during which time the married Jerry asks Charlotte to help him choose gifts for his two daughters. Charlotte is touched when Jerry thanks her with a small bottle of perfume. Subsequently, Charlotte tells Jerry about her family and her breakdown and learns from his good friends, Deb and Frank McIntyre, that Jerry is unhappily married but will never leave his family. After the ship docks in Rio de Janeiro, Jerry and Charlotte become stranded on Sugarloaf Mountain and spend the night together. Having missed her boat, Charlotte stays with Jerry in Rio for five days before flying to Buenos Aires to rejoin the cruise. Although they have fallen in love, they promise not to see each other again. Back in Boston, Charlotte's family is stunned by her transformation. Her mother, however, is determined to regain control over her daughter. Charlotte's resolve to remain independent is strengthened by the timely arrival of some camellias. Although there is no card, Charlotte knows the flowers are from Jerry because he had called her by the nickname "Camille," and, reminded of his love, she is able to forge a new relationship with her mother. Charlotte eventually becomes engaged to eligible widower Elliot Livingston. One night, at a party, Charlotte encounters Jerry, who is now working as an architect, a profession he had renounced years before in deference to his wife's wishes. His youngest daughter Tina is now seeing Dr. Jaquith for her own emotional problems. Charlotte asks Jerry not to blame himself for their affair as she gained much from knowing that he loved her. This chance encounter forces Charlotte to realize that she does not love Elliot passionately, and they break their engagement, so angering Mrs. Vale that during an argument with Charlotte, she has a heart attack and dies. Guilty and distraught, Charlotte returns to Cascade, where she meets Tina. Seeing herself in the girl, Charlotte takes charge of her, with Jaquith's tentative approval. When Tina improves enough, Charlotte takes her home to Boston. Later, Jerry and Jaquith visit the Vale home, and Jerry is delighted by the change in Tina. Charlotte warns him, however, that she is only able to keep Tina with her on condition that she and Jerry end their affair. Jerry believes that he is responsible for her decision not to marry Elliot, but Charlotte reassures him otherwise, saying that Tina is his gift to her and her way of being close to him. Jerry then asks if Charlotte is happy and she responds, "Well, Jerry, don't let's ask for the moon; we have the stars."