“Who are you?” Henry asked. “You must know there's an investigation. We're closed.”
“You!” Henry said, heart thumping.
Thomas smirked, tilting his head to one side. “Me,” he agreed.
“I tried to help!” Henry insisted. "But no one would listen to me." He took a calming breath, trying to relax his features, trying to look less like a frightened boy. Thomas pointed to the window, then looked at him over his shoulder.
“Just returning the favor,” he said, then winked and dispersed into curling grey wisp that fogged the fourth pane and outlined a last word.
You Are Dead Too
[Edited to add few lines to clear up confusion for several readers]