Silver and Opals

During a trip to Hogsmeade, Harry, Ron, and Hermione encounter Mundungus Fletcher, who is selling stolen items from Sirius's house. Harry confronts him, but Mundungus Disapparates. Later, on the way back to Hogwarts, they witness Katie Bell being cursed by a cursed opal necklace. She rises into the air, screams, and collapses. Harry, Ron, and Hermione help, and Harry covers the necklace with his scarf. They report the incident to Professor McGonagall, who is skeptical of Harry's theory that Draco Malfoy is behind it, as Malfoy was in detention with her at the time. The attack is a clear attempt to smuggle a deadly object into the school.