Hermione's Research on R.A.B. and the Half-Blood Prince

PAGES: 635-637

Hermione tells Harry and Ron that despite extensive research in the library, she has not been able to discover who R.A.B. is, though she found some obscure wizards with the same initials. However, she reveals that she has learned that Severus Snape's mother, Eileen Prince, is the “Prince” referenced in Snape's chosen moniker, the Half-Blood Prince. This realization infuriates Harry as it further confirms Snape's betrayal.