Harry Potter spends its holidays at Dursley. One evening, whereas Harry is locked up in its room because his/her uncle and his aunt have guests, Dobby, an elf of house, emerges in the room of Harry. It wants to prevent Harry from turning over to the Poudlard school. The refusal of this last Dobby conduit to destroy a cake, made by aunt Pétunia for the guests. Harry is then condemned by his/her uncle and his aunt to remain in her room. In the night, the Weasley wire come to seek it with a flying car belonging to their father Arthur Weasley.

Harry passes the remainder of its holidays at Weasley. The day of the re-entry, Harry and Ron do not manage to reach the driving passage at Poudlard Express. They thus use the flying car to go in Poudlard. This generates consequences such as they miss being returned.

During the school year, Misses Tinea, Nick Quasi-Without-Head and certain pupils are petrified. A word is even found on a wall, painted with blood, saying : "the Room of the secrecies was open. Enemies of the heir take guard ! ". It is discovered that Harry speaks the fourchelang, the language of the snakes. However, only the heirs to Salazar Serpentard are ready to speak it. So all the pupils believe that Harry Potter is the heir to Salazard Serpentard and is thus that which reopened the Room of the secrecies and released the monster that it contained on the pupils.