A few moments before the end of the previous act, Orin appears before his father's body in the study. Ezra's face in death is another startling reproduction of the face in the portrait, resembling the "carven face of a statue." Orin's face in the candlelight resembles these in turn. As Orin addresses his father, Lavinia appears silently in the doorway.
"Death becomes the Mannons," exclaims Orin. For him, Ezra was always the "statue of an eminent dead man," cutting the living dead for the impropriety of their living. Lavinia locks the door and rebukes her brother: to think that Ezra boasted so highly of Orin's bravery. Orin grins bitterly. At the front, he would only volunteer for extra danger in fear of anyone discovering that he was afraid. He recalls killing a Reb face-to-face in the fog one night and then another just like him. The war meant murdering the same man again and again until he had killed himself. In his dreams, the faces of his victims change, becoming his, Ezra's, and others.
Orin continues and says that he got his wound at Peterburg when he walked out to enemy lines with his hand extended, deciding it would be a great joke on the generals if the soldiers suddenly reconciled. Once wounded, he went mad. His comrades joined him, and they captured a new part of the Rebel line. Lavinia urges him to forget and assures him she thinks him brave.
Frustrated, Orin changes the subject and tells Lavinia that Christine has already warned him of her madness. Lavinia implores him to listen, presenting Christine's pillbox and calling upon her father to make Orin believe. Orin dismisses her delusions saying that she has always been her father's daughter. He takes the box and puts it into his pocket.
Calculatingly Lavinia teases that Orin certainly would not let their mother's paramour escape. Orin flies into a rage, forcing his sister to his knees and commanding her to retract her lies. Lavinia calmly insists that she tells the truth, proposing that they watch Christine until she goes to meet Brant herself. Orin agrees to her plan.
Suddenly Christine knocks at the door fearfully. Lavinia commands Orin to feign that he has done as his mother wishes. As a test, she snatches back the pillbox and places it over Ezra's heart. Orin opens the door to a desperate Christine, who shrieks upon seeing the box. Orin laughs with savage irony, recalling how he believed he had returned to his island of peace. Christine is his "lost island." He stumbles out.
Stealthily Lavinia snatches up the box and marches out coldly. Christine implores her husband to not let her children hurt Brant. Reading an answer in the corpse's face, she rushes out in terror.
Act III provides Orin's account of the war, a war above all, as he tells Lavinia, symbolized by his father. Earlier we noted how the Civil War functions as a backdrop for the sibling rivalry that founds the Mannons' tragic fate. Here the war similarly appears as an allegory for the sexual drama afoot in the household. As Christine laments, war tears Orin from the "secret world" he shares with his mother and assumes his proper place within the Mannon line. Ezra and Lavinia imposes the service on him as his familial duty. His conscription is the assumption of the father's name and accession from the pre-Oedipal realm. Note Orin's fear of Ezra's wrath. This fear is greater that his fear of his demise at the hands of the rebels.
As noted above, this war is above all imagined here as a war between brothers, a war defined by sibling rivalry. Mourning's male players are all engaged such a rivalry, the son-lovers Orin, Brant, and Ezra vying for the desire of the mother. Their rivalries are murderously infantile, operating according to the logic of "either you go or I go." The result of Orin's delirious attempt to make peace with the enemy makes this inflexibility of this logic clear. For Orin, his service in his father's war means his destruction in one of these rivalries. As Orin tells Lavinia, he remained fearfully convinced that Ezra would outlive him and that the war would not end until his death.
As we have seen, because in these rivalries the other appears as that which stands in the self's rightful place, the men in battle here necessarily appear as each other's doubles. This doubling structures Orin's nightmare of his murders in the fog, where he repeatedly kills the same man, himself, and his father. This compulsive series of murders allegorizes the impossibility of the lover ever acceding to his "rightful place" within the Oedipal triangle, Mother will always want another, and producing yet another rival. The multiplication of death among these doubles also appears in the correspondences drawn between father and son in the stage notes. Ezra's mask-like face in death reproduces the portrait; this face resembles the "carven face of a statue"; Orin's candlelight face reproduces these in turn.
Despite Orin's misery, Lavinia, ever true to her father's name, refuses to hear his lament. Instead she insists that he must forget the war and that he can be assured of her pride in him. Though she would repress her brother's story, however, she knows to use his jealous rivalries against Christine. Despite Orin's eager readiness to believe his mother—note here his near- confiscation of the incriminating box—Lavinia knows she can goad him into revenging himself for his mother's "betrayal."
Notably the first demonstration of her mother's treachery involves a certain animation of the father's corpse. Not only does Lavinia enjoin the corpse to speak, but in placing Christine's box atop its heart, makes it her mother's accuser. Thus Christine enters into silent dialogue with the corpse at the close of the scene, reading an answer in the accuser's face.