Harry soon discovers that while some magicians, such as the school principal Headmaster Professor Albus Dumbledore, and Deputy Headmistress Minerva McGonagal can be kind and encouraging, others, like the sinister Professor Snape with his greasy black hair and nasty comments, are very hard to trust. One of the subjects that Harry really needs to learn is "Defense against the Dark Arts" but unfortunately, the teacher, Professor Quirrell, is such a bumbling and nervous man that he does not seem to be able to teach Harry very much at all.