Harry Potter and the Prisoner of Azkaban is my favorite book—and movie—in J.K. Rowling’s series. That means there’s a lot I love about the third Harry Potter installment, including the moment when Remus Lupin and Sirius Black are reunited in the Shrieking Shack.

The scene reveals a history that adds so much to the franchise and made Harry Potter feel like an even bigger, richer world. It quickly changes from Professor Lupin seemingly rescuing Harry, Ron, and Hermione from alleged murderer Sirius Black to a reunion between two old best friends. Like the trio, the reader at first might not understand the questions Lupin asks Black in the beginning but as the conversation unfolds their history, and by extension Harry’s parents’ history, is explained. We learn it wasn’t Black who betrayed them, but Peter Pettigrew. With Pettigrew and James, Black and Lupin made up the Marauders who created the map and the other three became Anamagi to help Lupin whenever he transformed into a werewolf. They all fought Voldemort, until one of them betrayed the rest.

It’s the little moments between Black and Lupin scattered within this sudden deluge of new information that always captivated me. The moments where they said just enough and yet left so much more unsaid! Things like Black silently confirming Lupin’s realization that they switched who was Secret Keeper without telling him and it clearly dawning on Lupin that for 12 years everything he thought about what happened with his friends was wrong. Black explaining what happened after over a decade with the anger of knowing his suspicions were incorrect and his choice led to his friends’ deaths as well as his imprisonment. The two asking each other for forgiveness for thinking the other was Voldemort’s spy.

Learning about all this built on what little we knew at this point about the first war with Voldemort and in doing so shifted how you thought about that time. It wasn’t just a clear-cut good versus evil conflict. Friends suspected friends, friends betrayed friends, and a group as close as Harry, Hermione, and Ron was torn apart trying to make the world a better place. I always felt this was the start of the series really opening up into a more complicated story where things get just that much darker than we’d seen before, leading the way for things to get darker for Harry and the others.

It was a great small bit of world building that would continue to be expanded on as the series continued and leaves you wishing Rowling would just write a Marauders book already! The scene isn’t as emotional in the movie and doesn’t go into quite as much detail as the book, but it’s still worth a watch as it manages to convey the core of the scene. Just promise me you’ll also check out the book version after watching it!