Seduction
The subject matter of the novel is a femme fatale, a beautiful woman who protects her identity in multiple ways, but she mostly protects herself by aligning herself with powerful men by way of seduction. The end of the novel sings this tune clearly when the doctor asks how a woman could bewitch a man without ever showing her face.
Plausible deniability
This book features an interesting incidence of what's called "plausible deniability," which simply means that someone's language or behavior allowed someone else to pretend they were innocent. This happens when the doctor finds that the murderess was likely the woman who charmed him with the blemish on her back. When he realizes it, he understands that the veil was to protect them both by plausible deniability.
Honor and shame
The main subject matter of the delicate and misbehaved novel is the Marquesa's affair that led to the praying-mantis-like behavior of murdering her lover. The murder, the veil, the blemish removal—all these are done to prevent the Marquesa's honor from being removed from her. Interestingly, it seems that some people already know that the Marquesa is up to no good, but without a reason to want her to be ashamed, everyone allows her to protect her honor by covering up her tracks. She truly is a femme fatale, because at the end of the novel, she's still at large, not because she has cleverly succeed, but because she has failed in such a seductive way that the doctor doesn't want to see her in trouble.
