Question: Alan Sidney Patrick Rickman was an English actor who gained wider notice for his film performance as a fictional character in a film series who becomes a double-agen on behalf of who? 
Sentence (from "Severus Snape"): A Professor at Hogwarts School of Witchcraft and Wizardry, Snape is hostile to the series' protagonist, Harry, the moment he sets foot in Snape's classroom; this hostility is rooted in Harry's resemblance to Harry's father James, who bullied and harassed Snape during their time at Hogwarts.
Relevant evidence: No