Act I
- The Octagon Room in Sir Robert Chiltern's house in Grosvenor Square
Sir Robert – a member of the House of Commons and junior government minister – and his wife, Lady Chiltern, are hosting a gathering that includes his friend Lord Goring, a dandified bachelor, Chiltern's sister Mabel and other guests. During the party, Mrs Cheveley, an enemy of Lady Chiltern from their schooldays, attempts to blackmail Sir Robert into supporting a fraudulent scheme to build a canal in Argentina. Her late mentor and lover, Baron Arnheim, induced the young Chiltern to sell him a Cabinet secret – which enabled Arnheim to buy shares in the Suez Canal Company three days before the British government announced its purchase of the company. Arnheim's payoff was the basis of Sir Robert's fortune, and Mrs Cheveley has Robert's letter to Arnheim as proof of his crime. Fearing the ruin of both career and marriage, Sir Robert submits to her demands. When Mrs Cheveley pointedly informs Lady Chiltern of Sir Robert's change of heart regarding the canal scheme, the morally inflexible Lady Chiltern, unaware of both her husband's past and the blackmail plot, insists that Sir Robert renege on his promise to Mrs Cheveley. For Lady Chiltern, their marriage is predicated on her having an "ideal husband"—that is, a model spouse in both private and public life whom she can worship; thus, Sir Robert must remain unimpeachable in all his decisions. Sir Robert complies with her wishes and apparently seals his doom.
Toward the end of Act I, Mabel and Lord Goring come upon a diamond brooch that Goring gave someone many years ago. He takes the brooch and asks Mabel to tell him if anyone comes to retrieve it.[10]
Act II
- Morning room in Sir Robert Chiltern's house
Goring urges Chiltern to fight Mrs Cheveley and admit his guilt to his wife. He also reveals that he and Mrs Cheveley were once engaged. After finishing his conversation with Chiltern, Goring engages in flirtatious banter with Mabel. He also takes Lady Chiltern aside and obliquely urges her to be less morally inflexible and more forgiving. Once Goring leaves, Mrs Cheveley appears, unexpected, in search of a brooch she lost the previous evening. Incensed at Chiltern's reneging on his promise, she exposes him to his wife. Lady Chiltern denounces her husband and refuses to forgive him.[11]
Act III
- The library of Lord Goring's house in Curzon Street
Goring receives a letter from Lady Chiltern asking for his help – a letter that could be misinterpreted as a compromising love note. Just as Goring receives this note, his father, Lord Caversham, drops in and demands to know when his son will marry. A visit from Chiltern, who seeks further counsel from Goring, follows. Meanwhile, Mrs Cheveley arrives unexpectedly and, misrecognised by the butler as the woman Goring awaits, is ushered into Lord Goring's drawing room. While she waits, she finds Lady Chiltern's letter. Chiltern discovers Mrs Cheveley in the drawing room and, convinced of an affair between these two former lovers, he storms out of the house.
When Mrs Cheveley and Lord Goring confront each other, she makes a proposal. Claiming to still love Goring from their early days of courtship, she offers to exchange Chiltern's letter for her old beau's hand in marriage. Lord Goring declines, accusing her of defiling love by reducing courtship to a vulgar transaction and ruining the Chilterns' marriage. He then springs his trap. Removing the diamond brooch from his desk drawer, he binds it to Cheveley's wrist with a hidden lock. Goring then reveals how the item came into her possession: she stole it from his cousin, Mary Berkshire, years ago. To avoid arrest, Cheveley must trade the incriminating letter for her release from the bejewelled handcuff. After Goring obtains and burns the letter, Mrs Cheveley steals Lady Chiltern's note from his desk. Vengefully she plans to send it to Chiltern as, ostensibly, a love letter from Lady Chiltern to Goring. Mrs Cheveley exits the house in triumph.[12]
Act IV
- Same as Act II
Lord Goring proposes to and is accepted by Mabel. Lord Caversham tells his son that Chiltern has denounced the Argentine canal scheme in the House of Commons. Lady Chiltern appears, and Lord Goring tells her that Chiltern's letter has been destroyed but that Mrs Cheveley has stolen her note and plans to use it to destroy her marriage. At that moment, Chiltern enters while reading Lady Chiltern's letter, but as the letter does not have the name of the addressee, he assumes it is meant for him, and reads it as a letter of forgiveness. The two are reconciled. Lady Chiltern initially agrees to support Chiltern's decision to renounce his career in politics, but Goring dissuades her from allowing her husband to resign. When Chiltern refuses Goring his sister's hand in marriage, still believing he has taken up with Mrs Cheveley, Lady Chiltern is forced to explain last night's events and the true nature of the letter. Chiltern relents, and Goring and Mabel are permitted to marry. Lady Chiltern reaffirms her love for her husband and says, "For both of us a new life is beginning".[13]
