The tale begins with a flashback to Maleficent as a young girl fairy, befriending a farm boy who's snuck into her forest on a mission of thievery. They grow close and continue to see each other, even after the king of a human stronghold on the outskirts of the forest tries to invade Maleficent's domain and then watches in shock as the heroine and her tree-warrior pals lay waste to his army. As teenagers, the fairy and the human share a silhouetted lip-lock on a hilltop—"true love's first kiss," in the Disney parlance. He stops coming around, breaking the girl's heart. Years later, the now adult Stefan (Sharlto Copley) overhears the now-dying king promising his realm to anyone who can kill Maleficent. And it's here that we head into the first of the film's magnificently disturbing sequences.
I've read reviews complaining that we don't know enough about Maleficent and Stefan's personalities, much less the details of their relationship, which means that Stefan's betrayal "comes out of nowhere," and so does not make dramatic sense. This is a fair description (or complaint); but to me, the lack of development makes the twist feel more like something that might happen in a fairy tale—not a clean-scrubbed Disney fairy tale in which every plot twist is clearly delineated, but an ancient story that kids might listen to, rapt and horrified, then interrupt to ask, "By why would the boy do that to someone he loved?", whereupon the adult storyteller would explain that sometimes people do cruel things to people they love because they want things.
In any event, we know what's really going on in the scene. After snuggling with Maleficent on a hilltop, Stefan gives her a drink laced with a sleeping potion, prepares to murder her after she's passed out, then has a failure of nerve. He slices off her wings instead, and brings them to the king as "proof" that he did as promised
