Harry Potter and the Prisoner of Azkaban isn't so much about forgiveness as it is about the difficulty of actually forgiving someone. Forgiveness and compassion are ongoing processes here, and they are things that don't come naturally to every character. Throughout the novel we're confronted with situations that may or may not be forgivable. Ron manages to forgive Hermione for her role in Scabbers's "death," but Snape doesn't get over the almost-deadly prank that James, Lupin, and Sirius played on him as schoolboys. Some things seem unforgivable, such as Peter's role in the death of Lily and James. But, as Harry's actions toward Peter demonstrate, even unforgivable acts can inspire mercy.