I don't need to read the book to figure out the plot. Books 1 to 7 all sum up in pretty much the same way:-
After an awful summer holiday at the Dursley's, Harry returns to his beloved Hogwarts, with the obligatory adventure or two on the way. On arriving at Hogwarts he discovers his foes have cooked up a dastardly plot which he is able to foil by means of wands, secret tunnels and cloaks of invisibility with a couple of trips into spooky forests. At the end there will be a big party and Harry and his friends - minus any deceased characters will be celebrated as heroes. The end.