Antonio and Delio are outside of the Cardinal’s window at his palace in Milan. Unbeknownst to Antonio and Delio, they are very nearby the Duchess’s grave, which is evidently right outside the palace. Delio notes that the location has an echo; throughout the scene, the “echoes” are words coming from the Duchess’s grave (probably an actor offstage or beneath a trap door). Antonio says that he loves the ancient ruins. He is reflecting on the history and the bodies that lie there when some of his words begin to echo, particularly his words about death.
Antonio is ready to confront the Cardinal in his chamber just like Ferdinand first confronted the Duchess. The eerie echoes of the Duchess add a sort of supernatural element to the play. They are all written such that they sound very similar to the final words of Antonio’s phrases, but there are some slight modifications to suggest that perhaps something supernatural is going on.
Antonio notes that the echo sounds like his wife’s voice, to which the echo says “aye, wife’s voice.” The echo seems to discourage him from going to see the Cardinal and tells him to be mindful of his safety, and it goes as far as predicting that Antonio will die. The echo also says that Antonio will never see the Duchess again, since he’s risking his life by going to see the Cardinal. Though Antonio doesn’t know it yet, here the echo is also implying that the Duchess is dead. Antonito resolves to take the risk of death and meet with the Cardinal. Delio says that he’ll take care of Antonio’s eldest son and come in as backup if needed.
The echo slightly modifies Antonio’s words to add a sense of dread and suspense to the play. It at once suggests that Antonio will soon die, and seems to signal to him that his wife is already dead. The echo is not as intense a theatrical device as a ghost, but it would have been extremely unnerving, especially since it would most likely have been voiced by the actor playing the Duchess.