Young Phineas Finn, just admitted to the bar, is tempted to postpone his career as a barrister by an offer to run for election as a member of Parliament from the Irish borough of Loughshane. Phineas’s father, a hardworking doctor, reluctantly agrees to support Phineas, as a member of Parliament receives no salary and can only hope that once his party is in power he will be rewarded with a lucrative office.

Phineas is elected. Among those to whom he says good-bye before leaving for London is pretty Mary Flood Jones, a girl devoted to Phineas but no richer than he. Phineas’s well-wishers in London include Lady Laura Standish, the daughter of Lord Brentford, an influential Whig. Phineas begins to fall in love with Laura and sees a rival in the aloof and unprepossessing but rich Mr. Kennedy, who is also a Whig and a member of Parliament. Laura tries to encourage a friendship between Phineas and her brother, Lord Chiltern, a violent young man who has quarreled with their father. Lord Brentford has made it clear that he will reconcile with his son if Chiltern marries rich, lovely, and witty Violet Effingham, a friend from childhood. Chiltern loves her deeply and has proposed repeatedly, but Violet is levelheaded and, although she is fond of Chiltern, does not intend to ruin herself deliberately.

At Laura’s recommendation, Phineas accepts an invitation to visit Loughlinter, the Kennedy estate in Scotland. Phineas makes friends there with several Whig leaders and becomes the special disciple of Mr. Monk, a cabinet minister with independent views. Phineas proposes to Laura, who tells him she is engaged to marry Kennedy. She explains that, against her father’s wishes, she has exhausted her personal fortune by paying her brother’s debts; she is consequently obliged to marry someone with money.

Last-minute fright prevents Phineas from carrying out his elaborate plans for his first speech in Parliament. Laura has been married for several months when she begins to find life with her strict, demanding husband oppressive. Chiltern, having once again unsuccessfully proposed to Violet, invites Phineas to hunt with him. During the hunt, Chiltern suffers an injury and Phineas takes cares of him; the two become close friends. Although he has no hopes for being successful with Violet, the young nobleman confides to Phineas that he will fight any other aspirant for her hand.

In the voting on the Reform Bill, the question of the ballot divides Parliament, and the government is dissolved. The capriciousness of Lord Tulla, who had ensured Phineas’s original success, prevents Phineas from running again for the Loughshane parliamentary seat. Lord Brentford, however, who has the English borough of Loughton “in his pocket,” offers that seat to Phineas, who is easily elected.

Phineas, who had rescued Kennedy from two attackers late one night, visits at Loughlinter again. Gradually, he has transferred his affections from Laura to Violet, but his plan to confide in Laura is prevented by her confession to him that life with her husband has grown intolerable. Phineas, despairing of an opportunity to see Violet, finds his excuse in a letter from Chiltern that contains a conciliatory message for his father. Phineas takes the letter to Lord Brentford, at whose house Violet is staying. Lord Brentford agrees to forgive his son if Chiltern resumes his courtship of Violet. Phineas sends this message to Chiltern; to avoid duplicity, he adds that he himself hopes to win Violet’s hand. He later finds the opportunity to propose to Violet. Although she rejects him, he feels that her negative answer is not conclusive.

Because Phineas refuses to give up his courtship of Violet, Chiltern challenges him to a duel. They fight secretly in Belgium, but word of the duel leaks out afterward, partly because of Phineas’s injury; he had been wounded before he could fire. At last, Phineas confides in Laura, who becomes angry—as much because of her own affection for him as because of her brother’s claims on Violet.

Phineas meets the beautiful and charming widow Madame Goesler, who becomes interested in him. Phineas had been left a legacy of three thousand pounds and soon receives an even more substantial income upon being appointed to an office that pays one thousand pounds annually. Laura feels that she has wronged Phineas and takes it upon herself to urge his suit with Violet. Violet, however, knows that Phineas originally courted Laura, and she dislikes being in second place. She refuses when Phineas proposes to her again.

Parliament passes the English Reform Bill, which redistributes parliamentary representation to conform to actual population. The seat for the borough of Loughton is among those voted out of existence. Because Phineas has proven an able and loyal Whig, he has been promoted to a higher office that pays two thousand pounds a year. Having no borough to run for, he despairs of keeping the office after the next election. Loughshane, however, is made available again by the caprice of Lord Tulla, and Phineas is assured of success.

Chiltern proposes to Violet once more and is finally accepted, and he and his father are at last reconciled. Miserable over Violet’s engagement, Phineas confides in Madame Goesler. He also tells Laura of his heartbreak, but she chides him, saying he will soon forget Violet just as he has forgotten her.

Lord Brentford finally learns of the duel between his son and Phineas, whom he accuses of treachery. Phineas discovers the real cause of Lord Brentford’s anger: Chiltern and Violet, quarreling over Chiltern’s unwillingness to work, have broken their engagement.

Madame Goesler has made a conquest of the elderly and widely respected duke of Omnium. Although tempted to accept, she finally refuses his proposal of marriage. Not the least of her motives is her attachment to Phineas. When Laura’s husband accuses her of having Phineas as a lover, Laura decides to leave him. Phineas again asks Violet to marry him, and she tells him that, although she and Chiltern have quarreled, she cannot love anyone else.

Phineas causes a great sensation at home by bringing Mr. Monk to Ireland with him. Caught up with Mr. Monk in political fervor, Phineas pledges himself to support Irish tenant rights in Parliament. Mr. Monk has warned him against such promises; he predicts that Phineas will be forced to resign his office if he votes in opposition to his party. Without means of support, he then will have to give up his promising career. Phineas confides in Mary Flood Jones about this danger and about his unsuccessful love for Violet. Phineas and Mary become engaged.

After Laura has taken up residence with her father, Kennedy seeks legal aid to force her to return to him. To escape persecution, she decides to live abroad. She confesses to Phineas that she has always loved him and worked for him, although she was heartbroken when he told her of his love for Violet. Laura urges him to ensure his career by marrying Madame Goesler for her money. Phineas does not mention his engagement to Mary. When Madame Goesler offers her hand and money to Phineas, he can only refuse. His first feeling is one of bitter disappointment.

Chiltern and Violet reconcile. The Irish Reform Bill is passed, abolishing Phineas’s seat for the borough of Loughshane—his career in Parliament is over. The intervention of friends in the government, however, results in Phineas receiving a permanent appointment as poor-law inspector in Ireland. It pays a yearly salary of one thousand pounds, enabling Phineas and Mary to plan an immediate wedding.