Sexuality in the monk.

The Monk: A Romance by Matthew Gregory Lewis was originally published in 1796. It was a typical novel of the “Gothic” genre, which was typified by dramatic, convoluted plots, horror, supernatural occurrences, and “damsels in distress.” One frequent element in the Gothic is a chaste, virtuous, noble (but often poor, powerless, or orphaned) young woman whose virginity is threatened by an evil, wealthy, powerful man.
In The Monk, sexuality is deeply intertwined with morality, with “good” women being chaste and immoral women being sexually predatory. Much of the novel revolves around dynamics of sexual control and morality, with virtuous women resisting inappropriate sexual advances, bad women displaying the vice of lust, and flawed but redeemable women partially yielding (albeit passively) to male sexuality—but themselves not actively soliciting sexual encounters.
Matilda is the evil woman and sexual temptress of the novel. She has quasi-magical powers, seduces the monk Ambrosio, and eventually is fully allied with Satan. From the moment she enters the monastery in male disguise as Rosario, she is portrayed as breaking the boundaries of sexual and gender conventions. The initial attraction of Ambrosio to Rosario flirts with themes of homosexuality. When Rosario is revealed as Matilda, her character continues to break conventions, such as the masculine exclusivity of the monastery and the role of women as subordinate and passive in sexual matters.
Agnes is a typical Gothic heroine and is in love with Don Raymond. Although she transgresses conventional sexual morality of the period by allowing herself to be seduced by her lover, she is redeemable in so far as they were planning to be married before she was shipped off to the convent. Within the plot, she is purified through extensive punishment and imprisonment and the death of her baby. This and her loyalty to her lover allow her to become a “good woman.” She is happily married at the conclusion of the novel without violating the audience’s beliefs about the immorality of fornication.
Antonia and Virginia are both also traditionally “good” women in so far as they are sexually pure. Virginia is a virgin, and Antonia only loses her virginity because of rape. In all cases, the religious setting of most of the novel emphasizes the link between religious morality and sexual control, with the convent and monastery serving as an apparent locus of both.
The trope of monasteries and convents as hotbeds of sexual immorality hidden under a pious exterior was a common element of English Protestant literature, which was often strongly anti-Catholic in this period.