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.