Upon his arrival in Europe, Christopher Newman begins to visit the various art galleries. In Paris, he meets, in the Louvre, a young girl who is making a copy of a great master. He prefers the copy to the original and offers to buy it. The young girl, Mademoiselle Noémie Nioche, sells it to him at a much higher price than it is worth.
While at the Louvre, he meets an old acquaintance, Tom Tristram, whom he knew during the Civil War. He tells Tristram how much money he has made since the war and about his decision suddenly to drop out of the business and travel in Europe. When he suggests that he is on the lookout for a wife, Tristram tells him that Mrs. Tristram could help him. After several meetings, Mrs. Tristram suggests that he should court Madame Claire de Cintré, a very proud and inaccessible young lady who comes from one of Europe's oldest aristocracies. Later, Newman accidently drops in and Madame de Cintré is just leaving. She extends him an invitation to visit her, but when Newman arrives two days later, he is told that she is not at home.
The next day, Monsieur Nioche brings Newman the completed copy of the painting and is engaged to help Newman with French. The mademoiselle is to do some more copies for him. In a few days. Newman leaves on a tour of Europe during which he meets with a young Unitarian minister from America. They compare their reactions to Europe and the young minister thinks that Newman is too liberal in his approach to life and art.
Upon his return to Paris, he calls on Madame de Cintré and finds her home. He also meets her brother Valentin and her sister-in-law, Marquise de Bellegarde. He apparently makes something of an impression on them. About a week later, Valentin pays Newman a visit. They discuss many aspects of European life, but whenever possible Newman brings the discussion around to Madame de Cintré. After a few more visits, the two men become good friends, and it is then that Newman tells Valentin that he wishes to marry Claire de Cintré. Valentin is shocked and thinks that Newman will not possibly be able to succeed, but promises to help him. Thus, after more visits, and as soon as possible, Newman proposes to Claire de Cintré. She is somewhat surprised and asks him to say no more about the subject for at least six months. Newman is encouraged because she didn't openly refuse him.
After the proposal, Newman meets the mother and the older brother, who are the head of the family. They are very cold and haughty, and look upon Newman as some type of curiosity. But at a later meeting, they tell him that he has permission to continue seeing Claire de Cintré.
One night at the opera, Newman introduces Valentin to Noémie Nioche. He tells Newman that the girl is not very honorable and that the girl's father knows this and consents to it. Newman is shocked and disagrees. Nevertheless, Valentin is intrigued by Noémie's flirtatious charms. He plans to see her some more.
Sometime later, at a dinner party, Newman is introduced to Lord Deepmere, a distant relative from England. Lord Deepmere seems interested in Claire de Cintré. After the six months have elapsed, Newman proposes once again to Claire de Cintré, and to everyone's surprise, she accepts him. He wants to give a party, but the Bellegardes say it is their duty. At the ball, Newman is introduced to all of the aristocracy of France. The grand duchess, the titular head of European society, is delighted with Newman, but Newman is so happy that he does not notice that Lord Deepmere spends all of his time talking to Claire de Cintré.
Shortly afterwards, Newman is at the opera when he notices the presence of Valentin and Noémie and another gentleman. After a talk with them, Newman leaves. He later discovers that Valentin is going to fight a duel with the strange man over Noémie. Newman cannot understand this.
The next time he calls on Claire de Cintré, he finds her about to leave for the country home. She explains that she had written him a letter, but now tells him in person that she cannot marry him. Newman feels that the older Bellegardes have gone back on their promise. He wants to follow Claire de Cintré, but he gets word that Valentin has been fatally wounded in the duel and he must go to him. He finds Valentin still alive and tells him what happened between him and Claire de Cintré. Valentin is ashamed for his family and tells Newman to go see the housekeeper, Mrs. Bread, who possesses some type of knowledge which, if used properly, would force the Bellegardes to keep their word.
Newman goes to Claire de Cintré and tries to persuade her to marry him in spite of her family, but she tells him that she is resolved never to marry, and is determined to become a Carmelite nun. Newman goes to the Bellegardes and suggests that he has information which could damage them if they do not live up to their side of the bargain. They refuse Newman. He then goes to see Mrs. Bread, the housekeeper who has always liked Newman and who is strongly attached to Claire de Cintré. She tells him of a letter that the old Marquis de Bellegarde wrote on his death bed, telling how the son and wife had withheld his medicine from him which caused his death. He charges them with murder. Mrs. Bread then accepts Newman's offer to come and be his housekeeper. She leaves the Bellegardes despite arguments and threats against her.
Newman goes to the convent where Claire de Cintré is an apprentice. While there, he sees the Bellegardes, and confronts them with the letter. They are visibly upset, and the next day, Urbain comes to Newman and asks him to relinquish the document. Newman asks for Claire de Cintré's hand in marriage, but he is once again refused. Newman then decides that he must take his revenge.
He plans first to reveal his information to the grand duchess, but in visiting her, he recognizes their great differences, and says nothing. Soon afterwards, he leaves Paris and goes back to America, still desiring revenge. Later, he returns to Paris and suggests to Mrs. Tristram that he has something that could make the Bellegardes' life unpleasant. He then throws the slip of paper in the fire and watches it burn.