Afterwards the sexual encounter, the protagonist is very distressed; Beauplaisir is very confused as to why she had pursued him if she did not intend to have sex with him. He thinks she might be afraid that he is unwilling to pay her, and offers her a generous amount of money. The protagonist reacts angrily to him giving her money, saying it cannot compensate her for what she has lost. She tells Beauplaisir that the only adequate compensation for her loss of virtue will is his love and fidelity.
Beauplaisir vows to be true to her. No longer believing she is a prostitute, he asks her who she is. The protagonist is still unwilling to reveal her true identity and risk losing her reputation, so she tells him her name is Fantomina. and that she is the daughter of a country gentleman. Beauplaisir thinks to himself that she will undoubtedly eventually end up as a prostitute, but does not say anything to this effect.
Beauplaisir does not leave until very late, and Fantomina makes him promise to return to her the following day. In the morning, she bribes a servant of the house to back up her story if she is ever questioned. She also explains that she will only be at the house while visiting Beauplaisir, but, should he come looking for her, he is to be told that she has just gone out. With these arrangements made to keep her secret safe and conceal her identity, she returns to her actual residence and tells her aunt that she had taken a short trip and been left unable to return the night before.
As she reflects on what has happened, Fantomina feels secure that she has protected herself: even if Beauplaisir proves untrue, she will never have to worry about being publicly shamed. As time passes, she does indeed seem to be successfully executing her plan. She regularly meets Beauplaisir, but tells no one about the affair. She conceals her identity so effectively that when she meets her lover while presenting herself as a well-born lady, he has no idea that she is the same woman he knows as Fantomina. He notices a strong physical resemblance, but this similarity only makes the affair more arousing to him.
The protagonist's initial reaction after the two have sex suggests that she feels deceived, manipulated, and used. It also shows the limits of the disguise she has adopted. She enjoyed being perceived as a prostitute when it gave her freedom and required her only to flirt, but she is offended at actually taking money in exchange for sex. Her demands of Beauplaisir reflect the resurfacing of a more traditional model of feminine behavior in the text. She feels that the two of them engaging in a loving and monogamous relationship is the only thing that will legitimize her sexual transgression, allowing it become an expression of love rather than a tawdry exchange.
Despite her hopes that the two of them will cultivate a genuinely loving relationship, the protagonist is unwilling to be fully honest with Beauplaisir. She does admit that her presentation as a prostitute was a ruse, but she replaces this lie with a different one rather than telling the truth. Even though she does love him, she doesn't trust him and takes care to make sure her identity will remain concealed. This strategic choice suggests that the protagonist has quickly become more worldly and cynical. Having seen how quickly a seemingly innocent plan came to have real consequences, she takes steps to protect her future by ensuring her identity remains concealed.
The protagonist also seems to quickly bounce back from having been placed in an unanticipated situation, and reshapes her relationship with Beauplaisir into something over which she has control. She is quick-thinking, persuasive, and discreet, and all of these characteristics allow her to set up a framework in which she can pursue the relationship with very little fear of detection. By doing so, she adopts a position traditionally occupied solely by men: she can pursue a pleasurable relationship with the partner of her choice and not suffer any negative social consequences as a result. In this way, the power balance between her and Beauplaisir seems to shift: he is the naïve and blissfully ignorant one, while she calculates and makes decisions that best serve her interest. What mihgt have begun as a relationship in which she was vulnerable quickly becomes one in which she arguably has the upper hand. Margaret Case Croskery points out that, at this point in the novel, "she remains remarkably safe from the loss of honor, financial ruin, and emotional harm which traditionally plague the maiden raped by a man who does not intend to marry her" (p.75).
The novel's central plot of deception certainly stretches credibility: it seems outlandish that Beauplaisir could regularly be having sex with a woman and then fail to recognize her under other circumstances. The idea of characters being tricked into having sex without recognizing someone's identity has roots at least as far back as Shakespeare, often in a theatrical tradition that Haywood would have been familiar with. The narrator does also point out that he recognizes a similarity between his mistress and the protagonist, but uses this as an opportunity to illustrate how much social norms determine perception. It would seem impossible to Beauplaisir that an aristocratic woman would freely seek out sexual pleasure in the way he has observed his mistress doing, and so he simply discounts the resemblance as coincidence. He does. however. find the fantasy of combining a reserved, off-limit object of desire with an open-minded and sexually available woman to be particularly arousing.