The school year is almost over, and while the students are busy taking exams, Harry is also convinced Voldemort is about to return and to come for him. There’s more details to the events that take place near the end of the film, but there’s nothing major missing.
In years to come, Harry would never quite remember how he had managed to get through his exams when he half expected Voldemort to come bursting through the door at any moment. Yet the days crept by, and there could be no doubt that Fluffy was still alive and well behind the locked door.
Some of the exams are typical of tests students take around the world, others include transfiguring a mouse into a snuff box and making a pineapple tap dance across a desk.
Harry did the best he could, trying to ignore the stabbing pains in his forehead, which had been bothering him ever since his trip into the forest. Neville thought Harry had a bad case of exam nerves because Harry couldn’t sleep, but the truth was that Harry kept being woken by his old nightmare, except that it was now worse than ever because there was a hooded figure dripping blood in it.
The scenes of the final exams are largely missing from the film, as well as the Gryffindor students gathering at the lake while Fred and George Weasley are tickling a giant squid. Harry’s scar is hurting him pretty badly by this point, and he has a feeling there’s something he forgot about, despite the fact that they’re done with their exams.
Suddenly, Harry thinks of something and they are off to see Hagrid. This is the same scene from the movie where they question Hagrid about his interaction with the hooded figure he got the dragon egg from. Once they know Hagrid gave the stranger information about Fluffy, they are off to tell Dumbledore. Unfortunately, he has gone to London after receiving an owl from the Ministry of Magic. They tell Professor McGonagall that they think the Sorcerer’s Stone is about to be stolen. She drops the books she’s carrying at the news that they know about it, then assure them that it’s well-protected and not to worry.
They decide that Snape is going to try to steal the Sorcerer’s Stone that night, since Dumbledore is away.
“Right, here’s what we’ve got to do,” he whispered urgently. “One of us has got to keep an eye on Snape — wait outside the staff room and follow him if he leaves it. Hermione, you’d better do that.”
“It’s obvious,” said Ron. “You can pretend to be waiting for Professor Flitwick, you know.” He put on a high voice, “‘Oh Professor Flitwick, I’m so worried, I think I got question fourteen b wrong… ’”
“Oh, shut up,” said Hermione, but she agreed to go and watch out for Snape.
But Professor McGonagall is onto them now, and chases Harry and Ron away from the door which stands between them and Fluffy. Snape also found Hermoine lurking about and she returns to the Gryffindor common room. After an impassioned speech by Harry, Ron and Hermoine say they are going with him that night, even though they know if they get caught it will be bad for Gryffindor. Points don’t matter; not when the stakes are so high.
After petrifying Neville, they make their way through the castle under the invisibility cloak. On the third floor, they encounter Peeves the poltergeist. Harry impersonates the Bloody Baron and scares Peeves off.
Harry uses the flute Hagrid gave him at Christmas to put Fluffy back to sleep. It’s evident someone had been there before them, but the beast is awake now and alert. They drop through the trap door, the beast only awakening when Hermoine stops playing it to drop through herself. The Devil’s Snare traps the two boys, but not Hermoine who frees them. They don’t drop through like they did in the film.
When it comes to the flying keys, all three of them ride broomsticks to try and find the right key. Because Harry is a Seeker on the Quidditch team, he is good at spying things while flying. He spots one key with a broken wing and figures it was already caught once before they got there.
When it comes to the Wizards Chess enchantment, the three of them have to actually be the pieces on the board, rather than riding them like they do in the film. They choose which pieces they will be and then stand on those squares while the chess pieces walk off of the board to the side. Ron plays the game until he must sacrifice himself so that Harry and Hermoine can go on.
After the Wizards Chess board, there is a mountain troll that, thankfully, is already knocked out so Hermoine and Harry don’t have to fight it. The next obstacle is potions lined up on a table.
Danger lies before you, while safety lies behind,
Two of us will help you, which ever you would find,
One among us seven will let you move ahead,
Another will transport the drinker back instead,
Two among our number hold only nettle wine,
Three of us are killers, waiting bidden in line.
Choose, unless you wish to stay here forevermore,
To help you in your choice, we give you these clues four:
First, however slyly the poison tries to hide
You will always find some on nettle wine’s left side;
Second, different are those who stand at either end,
But if you would move onward, neither is your friend;
Third, as you see clearly, all are different size,
Neither dwarf nor giant holds death in their insides;
Fourth, the second left and the second on the right
Are twins once you taste them, though different at first sight
Hermoine figures out the logic puzzle. Unfortunately, there’s only enough of the potion they need to go through the nest door for one of them. Harry will go on, while Hermoine will drink the one that will let her go back to Ron, and then send an owl to Dumbledore for help.
He drinks the potion and goes through black flames into the final chamber…..
Previous chapter (link): Harry Potter and the Sorcerer’s (Philosopher’s) Stone Chapter 15: The Forbidden Forest