"What I want you to do is to go in there and bring back the spellbook containing the Patronus Charm."
Lupin mentioning the book and what he wanted Harry to do[src]

The Patronus spellbook is a book with instructions and information on the Patronus Charm, owned by Remus Lupin.


Lupin used it during one of his Anti-Dementor lessons with Harry Potter. He placed the spellbook within a secret passageway accessed through the cupboard in Professor Cuthbert Binns's History of Magic classroom, and put a Boggart there also, knowing it would become a Dementor[1]. Harry took the book with him and presumably gave it back to Lupin afterwards.


Notes and references