Harry Potter is again spending his summer holidays with Mr. and Mrs. Dursley and their son. The Dursley's are again making his holidays a horror and Harry can't wait to return to school again. The reason the Dursely's hate Harry is becasue Harry is a wizard and his parents were also wizards. Both Harrry's mother and father were killed by Voldemart, a wizard gone bad, when Harry was just a baby and from that time he was forced to live with his only relatives, the Dursely's. However, the Dursley's never liked Harry's parents even though Mrs. Dursely's sister was Harry's mother. Despite this, the Dursley's and Harry must endure each others company druing the summer holiday months, and it is during this particular summer that Mr. Dursely's sister shows up for a visit.
Harry's aunt is a fat, pompous, obtuse woman who doesn't see any of the faults of her own family but constantly and publicly chides Harry at every turn. However, knowing Harry's abilities, Mr. Dursely makes a pact with Harry. If Harry will not use his magic for the entire visit he promises to reward Harry by signing a permission slip allowing Harry to be able to visit Hogsmeads Village near his school during the coming year. Harry subsequently makes it most of the way through his aunt's visit without one mistep until one day, she starts to talk condecendingly of Harry's dead parents in front of him and the Dursley's. This sends Harry over the edge and he lashes out at his aunt with a spell which makes her begin to swell. Finally she becomes so swollen that she starts to float, but Harry doesn't care other than to worry what will happen to him if the Ministry of Magic finds out that he has used magic in the Muggle wolrd, something forbade to all wizards and witches. Furious, Harry leaves the Dursely's house with a few possetions, including his pet owl and decides that he will not return.
As Harry is sitting on a curb, wondering what he is going to do next, he almost gets run over by a triple decker bus that stops right where he is.