The Christmas Polyjuice Scheme

On Christmas night, Harry, Ron, and Hermione execute their Polyjuice Potion plan. They successfully drug Crabbe and Goyle with sleeping potion-laced cakes and steal their hair. After drinking the potion, Harry and Ron transform into Goyle and Crabbe, respectively, but Hermione's transformation goes wrong because she used a cat hair instead of Millicent Bulstrode's, leaving her with a furry face and tail. Harry and Ron, now disguised, infiltrate the Slytherin common room and question Draco Malfoy. However, Malfoy reveals that he is not the Heir of Slytherin and does not know who is, though he boasts that his father knows about the last time the Chamber was opened. The mission is a partial failure, but they learn that the Heir of Slytherin is still at large.