Antagonist

Character Role Analysis

Sirius Black

We don't find out until the last act of the film that Sirius Black isn't a bad guy after all. Of course, we knew he was a good guy because we'd read the book first, but that's irrelevant here. Throughout the movie, Harry is motivated by the threat of Sirius Black. Harry knows that Sirius is an escaped killer who helped Voldemort. And now he's after Harry.

Sirius's presence is a shadow over Harry's entire third year at Hogwarts. Wanted posters with his grimacing mug are plastered on every wall. The Dementors are a presence reminding Harry that something even worse might be lurking out there looking for him.  And Harry isn't the type of person to just let a bad guy find him. All of his actions are motivated by Harry's desire to find Sirius, and to take revenge on him for killing Harry's parents. If you put a big button labeled "Voldemort" in front of Harry, you know he'd push it.