It is after dinner in the library of Lady Britomart Undershaft's house in January 1906. The high-tempered Lady Britomart sits at her writing table. Her son, Stephen, a grave young man who takes himself very seriously and is somewhat in awe of his mother, enters the stage. He asks his mother why she has called him. She asks him to wait and chastises him for beginning to read in the meantime and fiddling with his tie.
Britomart then aggressively announces that Stephen is now a grown man, well traveled and educated, and he must take charge of the family affairs. Though both his sisters are to be married, Britomart's income cannot sustain four households. Lomax, Sarah's fiancé, will not receive his trust fund until 35. Barbara, the most promising member of the household, has joined the Salvation Army and become involved with a tempestuous Greek scholar, Adolphus Cusins. Britomart cannot avoid the topic any longer—they must speak of Stephen's fabulously wealthy father, the great military industrialist Andrew Undershaft.
Stephen is all too aware of his father's wealth. He rarely opens a newspaper without reading of the latest weapon from the Undershaft and Lazarus firm. With his cannons and war loans, Andrew Undershaft has Europe under his thumb. He is above the law.
Britomart remarks that Undershaft has broken the law since birth, as his parents were unmarried. Like all the Undershafts before him, he was a foundling and, in the tradition of the armory, has disinherited Stephen to find a foundling as his own successor. Britomart divorced him as a result. She could not bear such an immoral man, a man who subscribed to a "sort of religion of wrongness."
Stephen is naïvely bewildered by his father's strange morality. Right should always be right, and wrong is wrong. He insists that they not ask for his father's assistance. Britomart resigns herself to asking Andrew. She has already invited him to visit this evening and meet the family and Stephen is outwitted and overwhelmed.
Britomart asks Morrison, the butler, to summon the family to the library. She warns Stephen against appearing nervous. It will only encourage his sister Barbara, a major with the Salvation Army, to try to get her way. Barbara and appear first and their respective fiancés follow.
Britomart announces Undershaft's imminent visit to the stupefied party. Barbara is amused and expectant: after all, her father has a soul to be saved like everyone else. Lomax blathers nervously. With sarcastic suavity, Britomart asks Cusins to translate Lomax's "vulgar" street dialect. She warns the children to be on their best behavior.
Major Barbara begins with a comic meeting between an aristocratic mother and her only son. Though Lady Britomart ostensibly invites her son to take charge of the family affairs, she has already made arrangements for Undershaft to come to the house and resolve them. Note how, as with her largely uncontrollable daughters, Britomart chastises Stephen for fidgeting, warns him against being on his best behavior, and displays other maternal behavior. Lady Britomart appears as the overbearing mother of a fatherless household.
As such a maternal figure, Britomart will figure in the play as the bearer of an increasingly antiquated sense of convention and familial loyalty. She is sympathetic in being the play's great lady: charming, witty, and aristocratically provincial in her perspective on the work. Hopelessly she will insist on propriety in a family not particularly invested in such social forms.
Here Britomart's insistence on propriety emerges most clearly in her disparagement of Lomax. As in many of Shaw's works, dialect figures as an especially vexed point of contention in the household. Largely deployed for comic relief, Lomax's speech is a caricature of the society man's English. A frivolous playboy, he spends much of the play delivering stunted and tactless exclamations. Lomax converses in what Britomart considers "schoolboy drivel," a "vulgar" street dialect that says little and requires translation into proper speech. It behooves the reader to follow these clashes over dialect closely. The importance of the difference between proper and improper English in the play will become clearer in Act II, when dialect raises a number of questions regarding class difference.
As we might expect, Lady Britomart objects to her ex-husband for his betrayals of convention, familial duty, and morality, having divorced him for his disinheiritance of Andrew. Prefiguring the elaboration of what Shaw terms Undershaft's "gospel," Britomart bemoans his "religion of wrongness" and his insistence on always living in an "unashamed" fashion. As her only response to the new system of morality Undershaft introduces is to turn away in disapprobation, her family will ultimately abandon her upon his return. Stephen will assert his majority and cast aside her to discuss his future with Undershaft alone. As we will see, though she may play the great lady, she cannot compete with a father who compels those around him as a great man.
A formerly tabooed subject of conversation in the household, Undershaft already appears here as a compelling, all-powerful father—a man who, in holding Europe under his thumbs and determines law, can in no sense hyperbolically liken himself to the Roman Emperor. As if Andrew's name were not enough, his son's exclamations make his phallic prowess rather explicit: "The Undershaft torpedo! The Undershaft quick firers! The Undershaft ten inch!" The father's almost pornographic name bears his power, referring to how his firm serves as Europe's foundation (or "under-shaft"). Moreover, as Britomart reveals, Undershaft has served as the provider for their family all along as well. Thus he already holds them in his power.
Also note that at one point Stephen bemoans being called the "Woolwich Infant" at school. The Infant was a British 35-ton rifled muzzle-loading cannon, constructed in 1870 and featuring a steel tube hooped with wrought-iron coils.