Apparently Neville heard Malfoy's story and told Professor McGonagall. She is furious, leading Neville with her. She takes fifty points per student from Gryffindor House and gives them detention. Everybody in school is angry at them (exept the Slytherin students) because they all wanted one of the three other houses to win the House Cup, and Harry, Ron, Hermione and Neville has lost Gryffindor a great deal of points at one time. About a week before exams, Harry overhears Quirrell and Snape talking, and they suspect that Snape now knows how to get by all the obstacles that are protecting the Sorcerer's Stone. The next morning they are told that their detention will be at eleven o'clock at night. Harry, Neville, Hermione and also Malfoy who got detention earlier have to go with Hagrid and Fang into the forbidden forest. They start following a trail of silver Unicorn blood. A unicorn has been hurt badly, the second time in one week since Hagrid found one dead last wednesday. Draco and Neville go with Fang, while Harry and Hermione go with Hagrid. Harry wonders if a werewolf could be killing unicorns but Hagrid says they're not fast enough. They encounter Ronan and Bane, centaurs. They do not respond to Hagrid's inquiry of the wounded unicorn.
They see red sparks in the sky, meaning the others are in trouble, and Hagrid speeds over there while Harry and Hermione wait on the spot. It only was Malfoy frightening Neville who shot the sparks. Now Harry has to go with Draco and Fang, while Hermione and Neville go with Hagrid. They find the dead unicorn. Suddenly, out of the shadows, a hooded figure comes crawling across the ground, and starts to drink the unicorn's blood. Malfoy screams, the creature comes quickly toward Harry who is transfixed to the spot. Harry feels a screaming pain in his forehead, as if his Scar was on fire. After a while he comes to and finds a centaur standing over him. His name is Firenze.
While he takes Harry back to Hagrid he explains that drinking unicorn blood is a monstrous thing to do. That from the moment the blood touches the lips of the one who slayed the beast, he will lead a cursed life. He goes on to tell Harry that only someone who is desparate and needs the blood to stay alive long enough to drink something else to keep him alive would do that. Harry understands that it must have been Voldemort, needing enough time to live to get the Elixer of Life. They go back to the castle.
- David Bradley - Argus Filch
- Daniel Radcliffe - Harry Potter
- Emma Watson - Hermione Granger
- Maggie Smith - Minerva McGonagall
- Matthew Lewis - Neville Longbottom
- Rupert Grint - Ron Weasley
- Sean Biggerstaff - Oliver Wood
- Ian Hart - Quirinus Quirrell
- Tom Felton - Draco Malfoy
- Robbie Coltrane - Rubeus Hagrid
- Tom Baker - Ronan
- Jack Davenport - Bane
- Ewan McGregor - Firenze