Sexuality in Rebecca is complicated and plays an important role in the plot of the story.  Several characters are presented as having "deviant" sexual desires, including Jack Favell and Rebecca herself, whose sexuality has been described as "multifaceted" and "voracious" (Horner and Zlosnik 109). Maxim hates Rebecca for her unusual sexual activities, and she is ultimately murdered for her sexual transgressions. 

Rebecca is a dangerous character because she challenges cultural norms about proper sexual behavior.  We are explicitly told that Rebecca engaged in multiple affairs throughout her marriage, including an incestuous relationship with her first cousin. Rebecca is associated throughout the books with azaleas, and her clothing still smells like the flowers even after her death.  Horner and Zlosnik write that azeleas symbolize "an exotic female adult sexuality" (107).  They also suggest that Rebecca's signature, with its "tall sloping R," can be seen as representation of the shape of the female body (107). Alison Light argues that Rebecca's sexual behavior was a threat to the social order (15).  In a patriarchal society, women exchange their bodies for social status (15).  By treating sex as a "game", Rebecca undermined this system (17).