As O'Neill repeatedly indicates in the stage notes, the townsfolk function in Mourning as a chorus of sorts, serving as human backdrop to the major players.
Unlike O'Neill's other choruses, Mourning's are not, as Bogard notes, "diagrammatically conceived" as a "symbolic unit." A good example of what Bogard considers O'Neill's "diagrammatically conceived" choruses are the bar patrons in The Iceman Cometh, all of whom are driven by the major thematic conflict over the "pipe dream."
Here, the chorus largely only sets the scene for the events that follow. Mourning's gossipy choruses, filled with what Travis Bogard describes as "small town civic type" like carpenters, sailors, clerks, doctors, gossips, visiting cousins, business men, ministers, are peripherally aware of what transpires in the Mannon household. From the chorus, for example, we learn of Lavinia and Christine's response to Ezra's death, Orin's imminent arrival, and that fate is driving this tragedy forward.
Two major scenes follow the exchange between the townspeople, one involving a private conversation between Christine and Hazel and another involving Orin's return. Here the frantic Christine invites Hazel to become her co-conspirator against the Lavinia, a Lavinia who persecutes her with her constant, silent, and sentry-like surveillance. Christine imagines the somewhat one-dimensionally virtuous Hazel as that which she once was: young, innocent, loving, and trusting.
As noted above, the aging Christine is obsessed with the fantasy of a time prior to the father intervention into the mother-son dyad. In this act, Ezra's call to war stands in for this paternal intervention, tearing Orin from Christine's embrace. Christine projects this innocence of the pre-war past onto Hazel and entrusts her with Orin. Certainly, as Orin will observe in the following act, this stratagem is calculated to free herself of her son. More importantly, Christine can brook giving Orin to Hazel as she narcissistically imagines Hazel as a version of herself.
Orin, however, returns from the war in hopes of establishing paradise with his mother anew. Thus Orin pouts with disappointment when Christine is not there to meet him. His resentment for his father is clear and jealously over Brant is readily clear. As we will see, the recreation of Orin and Christine's "secret world" will quickly prove impossible. Orin returns from his father's war a changed man: he is no longer his mother's little boy. The war tears him from the universe of peace, life, and security he shares with Christine, plunging him into a struggle to the death with his fellow men. As discussed above, this struggle, a struggle that makes Orin capable of murder, allegorizes the rivalries the male players stage over the beloved Mother.