Harry Potter and the Prisoner of Azkaban · Chapter 10
Harry Learns Black Betrayed His Parents
Using the Marauder's Map to sneak into Hogsmeade, Harry overhears the Three Broomsticks conversation revealing Sirius Black was his parents' Secret-Keeper and betrayed them to Voldemort.
Outcome
Harry's hatred for Black intensifies; he vows revenge, deepening his emotional turmoil.
