The book begins by introducing Mr. and Mrs. Dursley, and their baby son Dudley. They live on Privet Drive and try to act as normal as possible. However, we soon learn that the Dursleys are hiding something.
What they're hiding is the Potter family; Mrs. Potter is Mrs. Dursley's sister, and the Dursleys try to pretend the Potters don't exist.
The narrator says that they don't realize how unusual this particular day is going to be – they don't see an owl fly past the window. But as Mr. Dursley leaves for work, he thinks he sees a cat reading a map, just for a second.
Mr. Dursley tries to forget about it, but then notices that there are people all around wearing cloaks. He thinks it's weird, and puts his mind towards work. At work that day, he doesn't look out the window, so he doesn't see the massive groups of owls flying about, which would strike anyone else as unusual.
During his lunch break, he ventures outside and sees a bunch of people in cloaks again. He overhears them talking about the Potters and gets really freaked out.
He almost calls his wife to talk about it, but then tries to convince himself that the cloak people probably weren't talking about his relatives.
On his way out of the office that evening, he bumps into a man wearing a violet cloak. The man tells him that You-Know-Who is gone and calls Dursley a Muggle. Mr. Dursley doesn't understand any of this, but it freaks him out all the same. When he gets home he sees that same cat outside his house.
That evening, he and his wife act normally. They hear on the news that the country is overcome with owls and that the sky is full of shooting stars.
Mr. Dursley asks his wife about the Potters, because he thinks they might be connected with all the weird happenings, but she hasn't heard from them. As they're going to bed, he sees that cat outside again. He falls asleep thinking about how the Potters shouldn't bother them.
Outside, the cat waits until almost midnight, when a thin old man in a cloak appears: Albus Dumbledore.
Dumbledore takes something out of his pocket, which looks like a cigarette lighter. He uses it to put out all the lights on the street. Then he walks over to the cat, which has transformed into Professor McGonagall. He knew it was her even when she was still a cat.
He asks her why she wasn't getting happy with the others. She says that she was worried about how risky everyone was acting and that the Muggles might notice something.
Dumbledore says it's been eleven years since they felt like this. They talk about how the Muggles can't find out about them, before confirming that You-Know-Who is definitely out of the picture.
Dumbledore eats lemon drops and says they should call You-Know-Who by his real name, Voldemort.
McGonagall says he's the only one who can say that, because Voldemort's only ever been scared by Dumbledore. She wants to talk about what really happened and how he was actually defeated.
She asks about the rumor that the Potters are dead, but their little boy, Harry, is still alive. Dumbledore confirms that it's true.
McGonagall says that Voldemort was defeated when he tried to tried to kill Harry and couldn't – that it stopped his power from working somehow.
Dumbledore says they'll never know how it happened, checks his mysterious watch, and says Hagrid's late. He says they're going to leave Harry with his family, the Dursleys, and McGonagall says they're despicable. Dumbledore counters that they're the only family Harry has left, and he'll be safest with them, even though they're unlike the magicians and his parents. He's written them a letter to explain.
McGonagall tells him that Harry's going to be a superstar, and Dumbledore says it's better for him to grow up modest and humble.
They're interrupted by Hagrid's arrival on a motorcycle. Hagrid is a gigantic man, but he's carrying baby Harry very carefully.
Harry is a tiny, black-haired baby with a lightning-shaped scar on his forehead.
Hagrid says goodbye to the baby and starts crying.
Dumbledore leaves Harry on the doorstep with a letter. The three magic people look really sad. As they vanish into the night, Dumbledore wishes him good luck.
The baby sleeps, as magic people think of him and toast his welfare.