At the very end of Other Voices, Other Rooms, Joel sees the "queer lady" in Randolph's window. Randolph, his evil cousin, who has engineered the trap that makes it impossible for Joel to ever leave the landing, likes putting on a giant white wig and dressing as a woman. The first time Joel sees her he hasn't met Randolph yet and doesn't know which window she is waving from; at the ending, though, it's pretty clear who she is.
The last lines of the novel are about the lady and Joel:
She beckoned to him, shining and silver, and he knew he must go: unafraid, not hesitating, he paused only at the garden's edge where, as though he'd forgotten something, he stopped and looked back at the bloomless, descending blue, at the boy he had left behind. (3.12.58)
The lady is like a siren, calling to sailor Joel. He doesn't feel like he has a choice; from now on, he belongs at the Landing.
This is a contrast to the way Joel used to feel, when he tried desperately to send letters to his aunt begging her to save him or even to run away with Idabel. Now he is "unafraid" and understands that he must stay with Randolph. He does look back, though, "as though he'd forgotten something." What he's forgotten is whom he used to be. Joel has transformed from the boy he was into a resident of the Landing.
He also—and this is more important—is implied to have left his innocence behind (before those hormone-ridden teenage years) and embraced his sexuality. By following Randolph, he's following in Randolph's manicured footsteps. It's unclear whether Randolph is gay, bisexual, genderqueer or just a dude who feels gorgeous in a kimono, but he's surely not a macho macho man like he was supposed to be according to early 20th Century Southern mores. Joel is telling the reader, as blatantly as way allowed in 1948 popular fiction, that he's here, he's queer, and everyone needs to get used to it.