Harry stops Dobby from blowing up the school.
Harry Potter turned around and saw Hermione and Ron standing there. They looked worried. Dobby had just been seen carrying two huge barrels of gunpowder up to the Gryffendor tower. They followed him up the stairs and heard him muttering "Nasty Mudblood powder. Only one way to get rid of the stuff is to burn it." He had put the barrels down and had taken out the candle and was about to put it into the barrel when Harry put a stupefy spell on him.
"That was close." said Ron.-