Thanks for satisfying my curiosity by posting the words of the ballad. It's clear how some of it relates directly to the plot of Pamela Dean's novel. ALthough the middle sister (Gentian) is the protagonist, it is indeed the eldest (Juniper, in the novel) who "lets him in." The boy next door is clearly non-ordinary in some way, probably supernatural, and, one suspects, dangerous. How closely the ending will relate to the riddle ballad, I don't know, but I'm almost there. Readers' opinions of this book on Amazon vary widely; some loved it, others thought it was far below Dean's other work in quality. I stand with those who find it enthralling. I enjoy her portrayal of gifted, literate young people and find it as fascinating here as I did in her TAM LIN. (One of the commentators said the characters reminded him/her of those in "a bad Madeleine L'Engle novel," a clear sign that I can discount this person's opinion. As far as I'm concerned, there IS no such thing as a bad L'Engle novel.) However, several people who liked the book overall found the ending rushed, incomplete, and unconvincing. So I am bracing myself to be let down .