Summary
A dumb show reveals that Alonzo has left town, and Vermandero chooses Alsemero to replace him as Beatrice-Joanna's husband. She and Alsemero marry.
DeFlores keeps seeing Alonzo's ghost everywhere he goes.
In Aslemero's bedchamber, Beatrice-Joanna discovers a potion labeled "M," for "maid," which tests whether a woman is a virgin. The instructions state that when taken by a virgin, the woman will gape, sneeze, laugh, and become sad. Beatrice-Joanna, worried that Alsemero will try this potion on her, offers Diaphanta payment to sleep with Alsemero instead. Diaphanta is excited by the idea given her attraction to Alsemero and the promised payment. Beatrice-Joanna tests the potion on Diaphanta, who has the appropriate response.
Rumors begin to circulate that Alonzo was murdered, and Vermandero suspects two noblemen recently escaped from the castle – Franciscus and Antonio. Tomazo accuses Vermandero of conspiring against his brother and vows to bring Alonzo's killer to justice.
Alsemero's friend, Jasperino, tells Alsemero that he heard Beatrice-Joanna flirting with DeFlores. Alsemero, concerned, asks Jasperino to fetch him his "M" potion. When Beatrice-Joanna arrives, Alsemero makes her drink the potion, and she feigns the same reaction that Diaphanta had. Alsemero is satisfied and overjoyed.
At the madhouse, Isabella, frustrated with all the suitors, decides to take up a rouse of her own. She dresses as a madwoman and approaches Antonio, who rejects her. When she reveals her true identity, she accuses him of never truly loving her.
In Isabella's absence, Lollio promises both Antonio and Franciscus that they can have Isabella if they can eliminate the competition – each other. They both agree.
Meanwhile, Alibius asks Lollio to bring Isabella to the performance at the castle.
Analysis
This section of the play reiterates the transactional economy that motivates many of the characters and ultimately breeds destruction among them.
Diaphanta is the innocent counterpart to Beatrice-Joanna; she is a virgin who happens to fawn over Alsemero, so when Beatrice-Joanna offers her the opportunity to make money and sleep with Alsemero, she is delighted by the request. This is, of course, the primary "changeling" plot present in the play: Beatrice-Joanna attempts to substitute Diaphanta for herself on the wedding night, fearful that Alsemero will discover she is not a virgin.
Such a ludicrous plan was not uncommon on the early modern stage. In fact, this was known as a "bed trick," in which characters were deluded into sleeping with someone under the pretense that they were someone else. Bed tricks helped drive plots along and often led to climactic revelations.
In The Changeling, however, the bed trick serves to underscore the commodification of women's bodies, and women's virginity in particular. Both DeFlores and Alsemero – seemingly disparate characters – are obsessed with the notion of Beatrice-Joanna's virginity, so much so that they are willing to kill to "possess" it (DeFlores) or test her with a potion (Alsemero). That the "changeling" plot of the play revolves around virginity and purity suggests that characters – women included – see female sexuality as something that is inherently dangerous and must be controlled.
However, the substitution of Diaphanta for Beatrice-Joanna, while the most apparent example of a "changeling" plot, is not the only one that occurs in the play. Indeed, Beatrice-Joanna successfully dupes Alsemero into thinking she herself is a virgin by mimicking Diaphanta's reaction to the potion. This rather silly experiment – in which a woman gapes, sneezes, laughs, and is saddened in response to the potion – suggests just how easy it is to hide one's true nature, a theme that has been gradually building over the course of the play. This theme is underscored by the comic subplot in which Isabella simply dons a disguise as a madwoman and is suddenly rejected by her former suitors. Through these various disguises, substitutions, and deceptions, the play emphasizes the difficulty of knowing someone's true intentions with certainty, and suggests that even the unquestionable results of "science" (i.e., the potion experiment) are not to be trusted.
