Beatrice-Joanna's Caution
When Beatrice-Joanna and Alsemero first encounter one another, Alsemero is blinded by his affection for Beatrice-Joanna and showers her in compliments. Beatrice-Joanna, in turn, warns Alsemero not to trust his eyes to convey the truth about a person. While Beatrice-Joanna is simply speaking from the perspective of caution, she is also ironically commenting on her own treachery to come, when she will conspire with DeFlores to murder Alonzo.
The Conspiracy
Beatrice-Joanna is certain that she can simply pay DeFlores for murdering Alonzo, thereby avoiding an implication in the crime. In reality, however, DeFlores does not perceive himself as a hired hitman. Instead, he demands that Beatrice-Joanna sleep with him as proper payment, solidifying their now indelible connection to one another. In his speech, DeFlores surprises Beatrice-Joanna by informing her that they are more alike than different.
Alonzo's Death
Alonzo's death – and Diaphanta's, for that matter – is an example of dramatic irony. The audience is well aware that DeFlores is responsible for the murders, but the majority of characters do not suspect any foul play from him. Even Tomazo, Alonzo's brother, takes a liking to DeFlores as he attempts to find his brother's killer.
Star-Crossed Lovers
The end of the play features the concurrent suicides of DeFlores and Beatrice-Joanna. In many ways, this ending satirizes the notion of star-crossed, ill-fated lovers (as one had seen earlier in the era in plays like Romeo and Juliet). Beatrice-Joanna and DeFlores are a perverted version of this paradigm brought together by crime and deception, and they die together as a result of their connected fates.
