As he walked, Harry trailed his fingers along the walls, spreading fire in his wake and humming under his breath. Vernon had finally succeeded in breaking him, had snapped his sanity like he'd snapped his bones, and Harry was tired of playing nice. Magic, uncontrolled and wild, sprang up behind him and thudded with impact, then he turned to see Vernon staring at him with fear in his eyes. "What's the matter, Uncle? Isn't this what you wanted? To see me broken? To watch me bleed?"
He stepped forward, then laughed cruelly as Vernon paled drastically and fell onto his backside. It was funny, especially since Vernok himself had caused it. Leaning down, magic still crackling around him protectively, Harry grinned and lowered his voice. "You should be careful what you wish for, Uncle Vernon... In your next life." Straightening, he stepped back and shivered as the heat of the flames licked harmlessly against his skin. They'd been created by his magic, were controlled by it too, so he was in no danger; not anymore.
"Goodbye, Uncle. May you rot in hell." With Hedwig dead and most of his possessions burned several weeks before, Harry had nothing left to his name except the clothes on his body and the magic crackling around him like a barely restrained feral animal. At least it meant he could walk out of the house, still trailing fire as he went, and into the shadows of the back yard. He heard screams then, three different tones, and grinned as he moved away from the house.
There was somewhere he needed to go, someone he needed to see, and someone he needed to kill. He couldn't do that from Privet Drive.