While The Heart Is a Lonely Hunter isn't exactly brimming with sex scenes, sexuality and sexual politics are strong undercurrents throughout the novel. We have Copeland's past domestic violence, Mick's blooming sexuality, and most notably, the curious case of Biff Brannon. Sexuality provokes fear in our characters, in addition to desire. They move back and forth between embracing and giving into their sexuality and being ashamed of it.
Sexual identity is constantly in flux in the novel, for all the characters.
Sexuality is an incidental or relatively minor detail for the majority of the main characters in the novel.
Mick's first sexual experience is part of her larger story of growing up.