In the third part of the play, O'Neill use of dramatic irony heavily drives the plot and demonstrates the mounting tension. In this final act, the conflict is driven by the fact that the audience and most of the characters know that Abbie’s new baby is Eben’s and not Cabot’s, but Cabot himself does not know this. In the party scene, the townsfolk all ridicule Cabot as he makes a fool of himself by dancing and drunkenly ranting. In response, the Fiddler slyly comments:
Ye’re the spryest seventy-six ever I sees, Ephraim! Now if ye’d on’y good eyesight…!
The audience and the Fiddler share insider knowledge at Cabot’s expense, ridiculing him for not knowing the truth about the baby. The Fiddler ironically jokes that Cabot is a spry dancer but lacks good enough eyesight to notice the infidelity occurring right under his nose. This, in turn, highlights Cabot’s flaws and self-righteousness. After the Fiddler makes this statement, Cabot goes on to berate the guests for being “too soft”—just as he berates Eben—and proceeds to dance wildly in front of the crowd.
Although Cabot begins the play as a formidable and intimidating figure, the Fiddler’s comment reduces him to a blind and unlikable old man. Furthermore, the use of dramatic irony sets up the plot for the incoming conflict between Cabot, Eben, and Abbie, as well as for the explosive and murderous conclusion of the play.
In the final line of the play, the Sheriff—who has come to arrest Abbie and Eben—makes a deeply ironic remark that serves as an example of situational irony:
(looking around at the farm enviously—to his companion) It’s a jim-dandy farm, no denyin’. Wished I owned it!
This concluding line of the play rings with irony, hammering home the themes of the play and the sense of hopelessness and a resigned mood. After watching the characters manipulate each other and even commit murder to own the farm, the Sheriff’s dismissive, casual comment is shockingly ironic to the audience—after all, the audience has seen just how much turmoil has come as a result of people wanting to own the farm. In turn, the Sheriff’s comment reveals the irony of the whole play: the characters have gone to such great lengths to own a farm that has only caused them pain throughout their lives. The Sheriff makes this comment "enviously," thus exhibiting the very emotion that motivated the characters to commit such extreme acts in the first place. Not only does this situational irony point out the hardships of farm life, but it illustrates that possessing something grand and beautiful—like the farm—does not actually make one’s life better, as we see with the downfall of these characters. The use of situational irony in the final line makes this clear to the reader.
