It's exam time. Harry is less worried about the exams and more worried that Voldemort might be about to return, and his scar keeps prickling. Suddenly, it occurs to Harry that it is highly suspicious that Hagrid long dreamed of getting dragon egg and then met a stranger who ''just happened'' to have one and be willing to gamble on it. They go to see Hagrid, who says that he got a dragon egg from a hooded stranger at [[Recap/HarryPotterAndTheOrderOfThePhoenixC16InTheHogsHead a pub in Hogsmeade]]. The stranger got Hagrid drunk and had a long conversation with him about dangerous beasts. Hagrid reveals that he let slip to the stranger that you can get past Fluffy if you play a bit of music ([[RunningGag "I shouldn'ta told yeh that!"]]).

Horrified, the trio rush off to find Dumbledore. They meet [=McGonagall=], who tells them that Dumbledore has gone away to deal with an urgent call from the Ministry of Magic. They explain that they know about the Philosopher's Stone. [=McGonagall=] is shocked, but insists the Stone is well-protected. When she goes away, they conclude that Snape has diverted Dumbledore away. They try guarding the third-floor corridor but [=McGonagall=] shoos them away. Feeling they have no alternative, and resolving that stopping Voldemort is more important than house points any day, they decide to go down the trapdoor that night.

On their way out of the dormitory, Neville stops and confronts them and demands that they do not get Gryffindor into any more trouble. Reluctantly, Hermione immobilises him with a Body-Bind Curse. On the journey to the corridor, they are almost given away by Peeves. But Harry impressively gets by impersonating the voice of the Bloody Baron, the one ghost that Peeves is afraid of. They arrive at the corridor and find it is already unlocked and someone has put Fluffy to sleep with an enchanted harp. They jump down the trapdoor and make their way through a dungeon filled with obstacles set by several teachers:
* Sprout's challenge: Luckily, there is a large tentacled plant covering the floor where they land. Less luckily, the plant immediately tries to strangle them. Hermione recognises the plant as the Devil's Snare and remembers in time how to stop it, by producing a fire.
* Flitwick's challenge: The next room is filled with flying keys, and has a locked door and several broomsticks. They realise they will have to catch the flying key, and take off on the broomsticks. Harry sees a key with a slightly damaged wing, deduces this is the right one, and uses his seeker skills to catch it.
* [=McGonagall's=] challenge: The next room contains a giant chessboard and they realise they will have to win a game to get across. The trio take the places of chessmen and Ron uses his chess skills to direct the game. A violent game with the animated chessmen progresses. They reach a point when Ron decides to allow himself to be captured by the opposing Queen in order to allow Harry to force a checkmate. Harry and Hermione reluctantly agree to the plan. Ron is knocked out when the Queen captures him, and Harry checkmates the opposing King.
* Quirrell's challenge: A troll. Luckily though, it has already been knocked out.
* Snape's challenge: A riddle involving potions. Magical fire blocks both the way back and the way ahead. There is a riddle to solve: there are seven potions on a table. One will allow the drinker to cross the magical fire to go onwards, and another will allow the drinker to cross the magical fire and go back. Three are poisonous and two are just nettle wine. Hermione solves the puzzle. The potion to go onwards only has a big enough dose for one person. They agree that Hermione should go back, rescue Ron and summon Dumbledore, while Harry will go onwards. He drinks the potion, walks through the fire into the next room and the die is cast...