Melodrama in Harry Potter

From Harry Potter and the Sorcerer's Stone:

“Look—” he murmured, holding out his arm to stop Malfoy. Something bright white was gleaming on the ground. They inched closer. It was the unicorn all right, and it was dead. Harry had never seen anything so beautiful and sad. Its long, slender legs were stuck out at odd angles where it had fallen and its mane was spread pearly-white on the dark leaves. 

Harry had taken one step toward it when a slithering sound made him freeze where he stood. A bush on the edge of the clearing quivered... Then, out of the shadows, a hooded figure came crawling across the ground like some stalking beast. Harry, Malfoy, and Fang stood transfixed. The cloaked figure reached the unicorn, lowered its head over the wound in the animal’s side, and began to drink its blood. 

“AAAAAAAAAAARGH!” 

Malfoy let out a terrible scream and bolted—so did Fang. The hooded figure raised its head and looked right at Harry—unicorn blood was dribbling down its front. It got to its feet and came swiftly toward Harry—he couldn’t move for fear. 

This particular passage struck me as melodramatic because it emphasizes the contrast between pure good and pure evil that permeates so many examples of melodrama. In this excerpt, Rowling uses a tragic example of pure good -- noted mainly for its beautiful, white appearance in contrast to the dark, ominous setting. Her description of the hooded figure includes what many would describe as a classic characterizations of pure evil -- surrounded by shadows, slithering, and crawling. This section of the book serves to introduce the two opposing forces of good and evil, setting the foundation for what is to come.

"Look--" he said, stopping Malfoy with his arm. They spotted a white unicorn lying on the ground in the distance. Upon closer inspection, they found it was dead. Harry took a step forward and heard a slithering sound that frightened him. A hooded figure came out of the bushes and reached for the unicorn, drinking blood from its open wound. Malfoy screamed and ran away with Fang while Harry stood still. He looked upon the figure in fear as it quickly came to him.