Harry Potter and the Prisoner of Azkaban · Chapter 2
Harry Inflates Aunt Marge and Flees
During Aunt Marge's visit, Harry's suppressed anger erupts and he accidentally inflates her like a balloon; he flees into the night with his trunk and Hedwig.
Outcome
Harry breaks from Dursley control and encounters the Knight Bus, learning of Sirius Black's escape from Azkaban.
