George Henderson asks casually about the quilt and the empty birdcage. Mrs. Peters says they think the quilt was knotted, and Mrs. Hale says she thinks the cat got the bird and ran away after Wright's death. Henderson reveals that they have found no signs of the murderer, and he and Henry Peters return upstairs. Mrs. Peters admits that when she was a girl, a boy killed her kitten, and she in return had wanted to hurt him, while Mrs. Hale wonders what it was like not to have children. Mrs. Hale suggests that the bird, a canary, would have sung in the manner of the young Mrs. Wright and that John Wright had caused both her and the bird to stop singing, with the implication that Minnie Wright killed her husband in revenge for the canary. The stillness of the house after the bird's death would have been awful, as Mrs. Peters notes. She says that "the law has got to punish crime," but Mrs. Hale recalls Minnie Foster and berates herself for not coming to visit and sympathize. They decide to pretend the fruit preserves had not been destroyed, and Mrs. Peters is glad the men heard nothing about their discussion of the dead canary.
When the men return, Henderson is explaining that they still have no motive, and he predicts that the jury will acquit a woman unless a clear reason can be established for this strange method of murder by rope. Henderson stays to continue looking for evidence, and after briefly looking at Mrs. Peters' pile of objects without seeing the box, he decides to trust her because "a sheriff's wife is married to the law." The sheriff and the attorney decide to look at the windows, while Lewis Hale exits, and the women look at each other. Mrs. Peters tries to put the box in her purse, but it does not fit. She manages to stuff it in her coat pocket before Peters and Henderson return. Henderson facetiously jokes that at least they know the blanket was quilted rather than knotted.
In the late twentieth century, feminists rediscovered and reinterpreted Trifles as a feminist work because it dealt with the themes of patriarchal oppression and female ability in the domestic arena. Although the men fail to recognize this search to understand female psychology, the events of the murder shock Mrs. Hale and Mrs. Peters into a new appreciation of their gender and of the need to support each other. Because she begins the play with a greater awareness of these issues, Mrs. Hale is first to articulate the commonality of the Midwestern female existence. She accepts partial responsibility for having driven Minnie Wright to the crisis that results in murder, and, in the climax of the play, she convinces Mrs. Peters to ally with her in spite of the law.
Of the two women, Mrs. Peters faces the larger paradigm shift when evaluating her role in the murder investigation. She never knew Minnie Foster as an unmarried girl, and as Henderson accurately notes, she is in a sense "married to the law." However, over the course of the play we learn that to identify Mrs. Peters solely by her husband's vocation is to misunderstand her life and her motivations, and, in the end, she indeed chooses to protect Mrs. Wright and forgo her husband's duty in favor of her role as a woman. She consistently modulates Mrs. Hale's resentful statements by apologizing for the men as doing what the law requires them to do, but the turning point in her thinking occurs when they realize that the messy stitching on one section of the quilt and the angrily half-wiped kitchen must have been a response to the canary's death. In twin moments of clarity, she admits aloud that she understands both the need for revenge and the power of loneliness, and she chooses to hide the bird.
Glaspell adapted Trifles into a short story entitled "A Jury of Her Peers," and accordingly Mrs. Hale and Mrs. Peters judge her murder of her husband and choose to forgive her rather than convict. Their choice implies that they find justice in Minnie Wright's decision to enact a suitable retribution on her husband for his strangling first of her life and then of her canary. Because of the women, we come to question the facts of the case, and our conclusion differs from that of the men. Nevertheless, the play does not describe the ultimate fate of Minnie Wright, and the possibility remains that the jury will still condemn her, even though she is a battered woman who has suffered immensely from her marriage. Similarly, we may choose not to consider her justified in her actions.
By the time the men return, they have found no worthy evidence and in addition have come no closer to the revelations made by Mrs. Peters and Mrs. Hale. Henderson has an intuitive sense for the evidence, as shown in his references to the quilt and the birdcage, but because he only looks at external rather than internal clues he fails to ascribe significance to the correct factor. He says, "It's all perfectly clear except a reason for doing it," suggesting that a panel of males, such as a contemporary jury, will never comprehend Mrs. Wright's motives, although they are by now clear to the audience. In a continued show of gender unity, the men jokingly patronize the women's involvement in the investigation; this time, the women prevail specifically because they are devalued and can therefore hide the evidence without questions from the men. They say the cat got the bird, a possible reference to the question "Cat got your tongue?" This phrase implies silence, but in this case, their silence reflects their refusal to speak rather than their verbal disempowerment at the hands of the men. The play ends on the pun "Knot it," which suggests that the women are "not it" and will not be pinned for murder because they have knotted away their knowledge - a reference to the bonds tying them together.
In Glaspell's writing of Trifles, she employs a number of techniques that have influenced later playwrights. The play has only one act, and five actors can perform it in half an hour, but she has structured the play in a very concise but effective manner so that it fully conveys its message. The characters' dialogue is also laconic and derives from the simple speaking patterns of Iowa, her home state; she employs dashes, pauses, and silences to convey as much as words. In addition, Glaspell makes use of mutual monologues, where two characters such as Mrs. Hale and Mrs. Peters talk in turn but to themselves rather than to each other - as when Mrs. Hale talks about children at the same time as Mrs. Peters’ admission of her childhood experience with the boy who killed her kitten. Theatrically, the mutual monologue was an experimental but useful dramatic device that Glaspell helped to develop. Finally, Glaspell's realism in depicting the lives of the early twentieth-century Midwestern woman give the play a powerful impact as it questions our assumptions about gender and guilt.