In Chapter 4, titled "The Keeper of the Keys," the narrative takes a pivotal turn as it introduces Rubeus Hagrid, the Keeper of Keys and Grounds at Hogwarts School of Witchcraft and Wizardry. The chapter begins with Harry Potter, who is still living with the Dursleys, facing increasing mistreatment and neglect. The Dursleys have gone to extreme lengths to prevent Harry from reading his acceptance letters from Hogwarts, which have been arriving in droves, much to their dismay.

On the eve of Harry's eleventh birthday, the Dursleys make an attempt to escape the letters by retreating to a remote shack on a small, deserted island. However, their efforts prove futile. Just as Harry is beginning to feel hopeless and unwanted, there is a dramatic entry by Hagrid, who bursts through the door of the shack, much to the shock of the Dursleys.

Hagrid is a giant of a man, both physically imposing and warm-hearted. He brings with him a letter that finally reveals the truth about Harry's identity as a wizard and his acceptance into Hogwarts. This is a moment of profound significance for Harry, who has spent his life unaware of his true heritage. Hagrid's presence transforms the atmosphere, as he is not only there to deliver the letter but also to confront the Dursleys about their treatment of Harry.

As Hagrid explains Harry's background, he reveals that Harry's parents, Lily and James Potter, were wizards who were murdered by the dark wizard Voldemort. This revelation is shocking to Harry, who had always been led to believe that his parents had died in a car crash. Hagrid describes how Voldemort attempted to kill Harry as a baby but failed, leaving Harry with a lightning-shaped scar on his forehead. This incident marked Harry as unique and famous in the wizarding world, a fact that Harry struggles to grasp at first.

Hagrid's explanation brings a mix of emotions for Harry—confusion, sorrow, and a burgeoning sense of belonging. He learns about the wizarding world for the first time, including the existence of Hogwarts, where he will learn magic and meet others like him. Hagrid's kindness and straightforwardness provide Harry with a sense of hope and excitement that he has never experienced before.

The chapter concludes with Harry feeling a glimmer of joy and anticipation as he prepares to leave behind the Dursleys and step into a world that is rightfully his. Hagrid's arrival not only marks the beginning of Harry's journey into the magical realm but also signifies a turning point in his life, where he can now explore his identity and destiny beyond the confines of his painful upbringing.