A dismayed Morrison announces Undershaft's arrival. A strong and gentle man, he appears slightly shy at finding himself in such a delicate situation. Failing to recognize Stephen, he greets Lomax and then Cusins as his son before realizing his error. He admits to a certain embarrassment. If he plays the part of the father, he will produce the effect of an "intrusive stranger"; if he plays the "discreet stranger," he will appear the "callous father." Britomart suggests that he is sincere and natural.
A painfully conscious pause follows. Lomax explodes into laughter when Barbara makes a funny face. Britomart threatens to throw him out. Barbara suggests that he fetch his concertina to entertain them. Undershaft then asks Barbara about her work at the Salvation Army. He notes that his firm could easily share the Army's motto: Blood and Fire. "My sort of blood cleanses: my sort of fire purifies" intones Undershaft.
When Barbara suggests that her father come visit the Army and sees its work firsthand, a scandalized Lomax protests crudely that salvation is not exactly Undershaft's line. Lomax tries, however, to be lenient toward Undershaft's work. He questions whether, in making war more destructive, his weapons facilitate war's quick end. Undershaft disagrees and states that war becomes more "fascinating" as it becomes more destructive. His morality and religion must have a place for cannons in it.
Stephen bristles at his father's sense of moral relativism. "There is only one true morality for every man" responds his father, "but every man has not the same true morality." Invoking Euripides, Cusins concurs. Stephen protests that some men are honest and others scoundrels all the same. Barbara counters that men are neither good nor bad but children of one Father.
Barbara and Undershaft strike a bargain. Undershaft will visit Barbara's shelter and Barbara his factory—each will attempt to convert the other to their cause.
Suddenly Britomart interrupts the discussion. If everyone is determined to talk about religion, they should do so properly. To everyone's amazement, an exasperated Britomart calls for prayers. Undershaft proposes a compromise, and says that Barbara should give a service in the drawing room. The family begins to move to the next room. A frustrated Britomart gladly sends Charles out but insists that Cusins stay. He responds that he could not bear to hear her make penance before the servants and departs. An offended Britomart retorts that she knows how Cusins has been systematically "humbugging her." She knows he has only joined the Army to worship to Barbara.
Left with Stephen, Britomart erupts into tears. She laments that the injustice of a woman's lot is that, after years of work, the father steals the children's affection. She joins the party in the drawing room; "Onward Christian Soldier" is heard on the concertina when she opens the door. Charles sullenly remains in the library.
Major Barbara is commonly grouped among Shaw's "discussion plays"—that is, plays that largely driven by discussion and oratory rather than more conventional forms of dramatic action. Similarly is Major Barbara also at times described as a play of ideas. Its discussions begin in earnest from here, with the meeting of the family in the parlor and its first encounter with Undershaft's gospel.
Undershaft makes his entrance into the household hesitantly, confessing his fear of appearing the "callous father" in playing the "discreet stranger." An indiscretion, however, is his first callous blunder, Undershaft failing to recognize his son. This joke on his protracted estrangement from the household marks his indifference to traditions of familial legacy. As he will later explain, the tradition of the Undershaft firm necessarily trumps that of the household: the identity of his son by kin is of little relevance to him.
Almost immediately after this blunder, however, the charismatic Undershaft establishes a rapport with his estranged family, the play recuperating a father whose children might consider callous into an engaging guest. The major point of contention that emerges here is Undershaft's competing system of morality, what Britomart describes in the previous scene as his "religion of wrongness." Note the reactions of his interlocutors. The heady Stephen bristles at even the suggestion of moral relativism; Lomax hems and haws in discomfort; Barbara remains unperturbed, certain she can save her father's soul. Only the Cusins assents to Undershaft's argument, betraying a fascination with his thought and foreshadowing his conversion to his gospel in the subsequent act.
Specifically, Undershaft poses his faith as a rival to Barbara's Salvationism, though the two are not without similarities. As he jests, the motto of the Salvation Army—"Blood and Fire"—could be his own. Undershaft begins to preach his gospel seductively. Here we only learn that it requires the war and destruction that he underwrites, war becoming more "fascinating" as it becomes more destructive. The destruction Undershaft wreaks seems to promise some form of redemption. Again, "My sort of blood cleanses: my sort of fire purifies" intones Undershaft enigmatically. Bemused by this preaching, Barbara makes a Devil's pact with her father that sets the ensuing action in motion. Each will engage in a campaign for the other's soul.
At this moment, an exasperated Britomart futilely strikes out against this decidedly unpleasant conversation. She does so in the name of propriety. If the family insists on discussing religion, she will call for family prayers. Her protest falls flat, however, the family abandoning her in disbelief for a service in the adjoining room. Britomart bursts into frustrated and cruelly comic tears, lamenting her children's betrayal. Thus Britomart already appears as the abandoned mother, excluded from and irrelevant to the moral struggles afoot between the other members of the cast—struggles that Undershaft, as the play's "great man," has introduced into the household.