Montraville and Belcour, two officers in the British army, are about to be assigned to America. They take a walk in the town of Chichester and see the beautiful Charlotte Temple, a fifteen-year-old boarding school student, leaving church.
The story describes how Charlotte's parents met. Her father, Mr. Temple, was the son of an earl and known for his charity. One day he was asked to help an honorable man in debtor's prison, Captain Eldridge. Eldridge went into debt to help his son, George, get started in the Navy, and was taken advantage of by his cruel creditor, Mr. Lewis. Eldridge has spent nearly two years in prison, and is supported by his faithful and kindly daughter, Lucy. Mr. Temple pays off Mr. Eldridge's debts, at great expense to himself, and marries Lucy, although this results in him being estranged from his family. Despite their reduced circumstances, the happy couple lives with Mr. Eldridge in a cottage, and has one daughter, Charlotte.
The narrative returns to the present day. Charlotte is a well-meaning but indecisive young woman. She is good friends with her promiscuous French teacher, Mademoiselle La Rue. One day, Mademoiselle La Rue brings Charlotte along on a visit to one of her suitors. As they cut through a field to get to the suitor's house, they are waylaid by Montraville, who has been looking for a way to see Charlotte again, and Belcour. Charlotte is charmed by Montraville's comments and accepts a letter from him. He bribes Mademoiselle La Rue to allow Charlotte to see him again.
Although Charlotte is initially uncomfortable with the older man's attentions, she continues to meet with him after being moved by his love letter. During these meetings, his friend Belcour strikes up a relationship with Mademoiselle La Rue. Meanwhile, Charlotte's parents plan a surprise birthday party for her at home.
One evening, Montraville explains that he is about to be sent to America, and he wants Charlotte to come with him, to get married there. He knows that he cannot marry her, because his family does not approve of him marrying a woman with no fortune, but is vague about his plans for the future. Charlotte initially agrees, but has second thoughts when she receives a letter from her mother asking that she come home for her surprise party. Under pressure from Mademoiselle La Rue, she meets Montraville intending to break up with him, but he convinces her to come to America with him. La Rue comes along, eloping with Belcour.
Charlotte writes a letter to her family explaining where she has gone, but Montraville destroys it, afraid that her parents will pursue them. Meanwhile, Charlotte's family and Captain Eldridge are heartbroken by her disappearance, and wait in vain for her to return after the marriage. They decide that they will forgive her and welcome her back into the family when she comes back.
On the voyage to America, an officer named Crayton falls in love with Mademoiselle La Rue. He proposes to her at the end of the trip, and she accepts; Belcour is not offended as he has realized she has a rotten personality and is glad to be rid of her. Charlotte is seasick throughout the voyage and bonds with Montraville as he takes care of her, but she begins to realize that Montraville could leave her at any time without marrying her, much as Belcour did to La Rue. When they arrive, Crayton introduces Charlotte and La Rue to his daughter (by his dead first wife), Mrs. Beauchamp. Charlotte feels great shame when Crayton introduces her as Montraville's mistress.
Montraville buys Charlotte a house outside of New York, and gives her an income and a servant. However, he rarely visits and she is consumed by loneliness. Meanwhile, Montraville is charmed by Julia Franklin, a young and pleasant heiress whose jewelry he rescues during a fire. Although he is more attracted to her than Charlotte, he feels bound to his young mistress and refuses to pursue Julia.
Belcour decides that he wants Charlotte as his mistress, and tries to sabotage her relationship with Montraville. He visits Charlotte and tells her about Julia Franklin, but she refuses to leave Montraville even though she is heartbroken. Mrs. Beauchamp, who lives in Charlotte's neighborhood, sees how sad Charlotte is. She decides to befriend Charlotte, even though it will endanger her own social status to associate with a fallen woman.
Mrs. Beauchamp goes to visit Charlotte, who has an emotional breakdown when she realizes someone actually wants to befriend her. She tells her neighbor her life story, and explains that she wants to go home to her parents but they don't respond to her letters. Mrs. Beauchamp senses that Charlotte's letters are being intercepted, and suggests that the girl send her mail through her from now on. Charlotte does so, composing a heartfelt, apologetic letter to her parents in which she also announces that she is pregnant. She begs to be allowed back into the family.
Montraville is deeply in love with Julia, but he will not leave Charlotte for her. Belcour tells Montraville that Charlotte has been unfaithful to him, and cements this by sneaking into bed with Charlotte while she is taking a nap and allowing Montraville to catch them that way. Montraville breaks up with Charlotte and refuses to see her again, but promises to send enough money for her and the child to live on. He then proposes to Julia, although he continues to blame himself for corrupting Charlotte and is plagued by feelings of guilt.
Back in England, Charlotte's parents receive her letter and are happy to hear from her. Mr. Temple goes to America to fetch her and the child and bring them back.
After Montraville is married, he recruits Belcour to administer Charlotte's finances and give her the money Montraville has set aside for her. Belcour keeps the money for himself, hoping that Charlotte will become financially dependent on him and become his mistress. However, Charlotte rebuffs him. When he announces that Montraville has married Julia, she becomes gravely ill from her shock, and Belcour is no longer attracted to her. He abandons her without giving her the money.
Charlotte recovers from her illness, but is evicted because she cannot pay the rent. She goes to visit Mrs. Crayton (Mademoiselle La Rue), who is now wealthy and popular. However, she declines to help Charlotte. Taking pity, one of Mrs. Crayton's servants, John, allows Charlotte to stay in his hovel so she does not die of exposure. There, she goes into labor, but becomes ill again after having the baby. He sends for a doctor, who informs Mrs. Beauchamp of Charlotte's situation. Mrs. Beauchamp, who has been out of town, does everything she can to help Charlotte but it is too late. Mr. Temple arrives just as Charlotte is dying, and promises to take care of her daughter.
After Charlotte's death, Montraville kills Belcour to avenge her, and lives a melancholy life with Julia. Mr. Temple brings Charlotte's daughter back to England, where he raises her along with Mr. Temple and Captain Eldridge. One day, they see a wretched hag in the streets. It is Mademoiselle La Rue, separated from Crayton and desperately poor. She apologizes to Charlotte's family for corrupting their daughter, and they take her to a hospital, but she dies shortly thereafter.
