Inciting Event: Just prior to leaving for Hogwarts, Harry is warned by Mr. Weasley that the escaped murderer Sirius Black is going to be coming after him. Promptly after, Harry is attacked by a Dementor—the guards of the Azkaban Prison, from which Sirius escaped—and rescued by the newly arrived Professor Lupin. Mr. Weaseley’s warning is properly the Inciting Event, since it primes the main conflict, but the story wisely follows up with a big “moment,” illustrating the danger.

First Plot Point: Honestly, there really isn’t a strong and obvious First Plot Point. Very shortly after the Dementor scene, Harry arrives in Hogwarts, which is still the obvious “adventure world” of the Second Act. His arrival doesn’t, however, have much to do with the main conflict, beyond Dumbledore’s announcement that the Dementors will be guarding the school.

Another First Plot Point candidate comes along when Harry’s tea leaves reveal the ominous “Grim,” symbolizing death. But this isn’t really new information, so much as it is a reinforcement of Harry’s previous sighting of the hound and Mr. Weasley’s warning about Sirius Black.

First Plot Point: The Fat Lady who guards Gryffindor’s dormitory goes missing from her painting. When she is discovered in another painting, she reveals she was moved there by Sirius Black, who has been inside the school. This is an obvious emphasis of the antagonistic force.

Midpoint: Harry uses his invisible cloak to visit the village and eavesdrop. He overhears that Sirius Black betrayed his parents to Voldemort, and that Sirius is, in fact, his godfather. He is shaken by this news and comes to a personal Moment of Truth when he vows to kill Sirius.

Second Pinch Point: The “Grim” appears and drags Ron off by the ankle, into a lair beneath the womping willow and then down the passage into the Screaming Shack in the village. Harry and Hermione follow, only to discover the Grim is, in fact, Sirius in animal form. It turns out Sirius wasn’t the betrayer and murderer—but rather it was the supposedly murdered Peter Pettigrew who has been masquerading as Ron’s beloved rat Scabbers all this time.

This is one of the biggest “new clues” I’ve ever seen dealt out a pinch point. It definitely emphasizes the antagonistic force, since this is actually the first time the protagonist even rightly understands who the antagonist is.

Third Plot Point: As everyone is trying to take Pettigrew into custody, the full moon turns Professoor Lupin into a werewolf. Sirius goes back into dog form to protect the children, and when Lupin nearly kills him, Harry rushes to his defense. Both Harry and Sirius are nearly killed by the Dementors—until a strange Patronus spell rescues them both. Sirius is then put into custody.

Climax: To save Sirius, Harry and Hermione use her “time turner” to go back in time. It turns out that they were instrumental in saving themselves earlier in the night (Harry himself was the one who cast the Patronus spell to save his earlier self and Sirius).

Climactic Moment: They free Sirius. This an interesting example of how, even though the Climactic Moment must be a definitive answer to the conflict question posed in the Inciting Event (“what to do about Sirius Black?”), it can still be completely surprising in its outcome.

Resolution: Lupin resigns over his werewolfism. Harry receives a wonderful new Quidditch broom from Sirius.