Later after the incident with Mrs.Norris, Harry, Ron, and Hermione put their heads together and discussed. They all thought that it was probably Malfoy who was the Heir of Slytherin. Around that same time Malfoy called Hermione a mudblood, and Ron vomited slugs.(Idk what happened first sry, If u find a mistake message me). They decided to brew a potion,to change in too three Slytherins to interrogate Malfoy. They decided to brew the potion in Moaning Myrtles bathroom and checked on it everyday. They needed some special ingredients so while Harry distracted Snape, Hermione went to Snape's cupboard to steal potion supplies. The potion took two months to brew so they set their plan in action during Christmas. They gave Crabbe and Goyle chcolate cakes that have sleeping potion in them. Then they hid Crabbe and Goylde and plucked their hairs. Hermione was a big fan of lockhart and during hid dueling club Hermione fought Millicent Bulstrode attaining her hair on Hermiones robes. As they drank the potion ron and Harry turned into Crabbe and Goyle, while Hermione turned into a cat. She stayed in the bathroom while the boys went. After that she went to the hospital wing.