5
Note the story's conflict. This means whatever is the main problem that the characters are having to overcome. It doesn't necessarily have to be a villain, like with Harry Potter and Lord of the Rings.
For Harry Potter, the main conflict is Voldemort's attempt to steal the Sorcerer's Stone and return to menace the Wizard World (and kill Harry).
For example, if you're summarizing The Odyssey, the main conflict is Odysseus trying to get home to Ithaca. Everything about the story is driven by his desire to get home and all the obstacles standing in his way.