After a hectic morning, the Weasleys, Harry, and Hermione all set off for King's Cross Station.
Arthur sticks close to Harry at the station and takes him aside to talk before Harry boards the train.
Harry tells Mr. Weasley that he overheard him discussing Black and that he isn't afraid.
But Mr. Weasley is still concerned and he tells Harry something odd: "Harry, swear to me you won't go looking for Black" (5.41).
Harry thinks this is bizarre.
Once on the train, Harry, Ron, and Hermione find a compartment occupied by a sleeping adult named Professor R.J. Lupin.
The trio decide he's pretty conked out and Harry tells his BFFs about the whole Sirius Black thing.
Ron and Hermione are freaked out about a lunatic murderer coming after their friend, but Harry thinks they should chill out.
The conversation then turns to the awesomeness of Hogsmeade, and Ron and Hermione are completely bummed that Harry never got his permission form signed.
Hermione lets Crookshanks out of his cage and the cat makes another go at Scabbers before settling down to glare at Ron.
Later, Draco Malfoy and his goons Crabbe and Goyle stop by to stir up trouble (some things never change), but they shut up and leave when they spot the sleeping Professor Lupin.
The train then slows and comes to a stop, which is weird. Then all the lights go out, which is extra creepy.
Neville and Ginny come into the compartment and Lupin finally wakes up and tells them all to shut up.
Then it gets very cold and something horrible comes inside: "Standing in the doorway, illuminated by the shivering flames in Lupin's hand, was a cloaked figure that towered to the ceiling. It's face was completely hidden beneath its hood. [...] There was a hand protruding from the cloak and it was glistening, grayish, slimy looking, and scabbed" (5.164).
The entire compartment gets cold and Harry hears a roaring sound, then screams, and then he passes out.
When he comes to, the lights are on, the train is moving, and the Dementor is gone.
Lupin gives Harry chocolate and goes to talk with the conductor.
Harry's friends are all shaken and afraid, but no one passed out like Harry did. No one heard screaming either...
Finally, the train arrives at Hogwarts and everyone makes their way up to the school.
Unfortunately, the news of Harry passing out has already made the rounds and Draco pops up to make fun of him, like a punk.
Lupin comes back and shuts Draco down, though.
As they enter the school, Professor McGonagall pulls Hermione and Harry aside and takes them to her office.
Harry is there to get checked over by the school nurse, Madame Pomfrey. He's humiliated and escapes as soon as possible, worried that he'll never live down his little fainting spell.
Hermione stays behind a few more minutes and then emerges with Professor McGonagall. The three make their way down the Great Hall for the Welcome Feast. They've missed the sorting hat, unfortunately.
Dumbledore delivers his welcome back speech, though it's more serious this year since he spends time warning people about the Dementors that are lurking about: "It is not in the nature of a Dementor to understand pleading or excuses. I therefore warn each and every one of you to give them no reason to harm you" (5.250).
Dumbledore moves on to happier matters and introduces two new professors. Professor Lupin will teach Defense Against the Dark Arts and Hagrid will teach Care of Magical Creatures.
Harry, Ron, and Hermione are psyched about Hagrid's new gig.
At the end of the feast, they rush up to congratulate Hagrid and then make their way to the Gryffindor rooms along with the rest of their house.