In the future...
Ron jumped up, startled, his eyes wide. "Bloody hell! Harry!" He gawped at the empty spot on Hermione's bed where Harry lay mere moments ago.
"Ron? What happened?" Hermione called from inside her wardrobe.
"Oh my bloody god, hell and pigs bums, Harry just- just- vanished! Evaporated! Pft! Gone!" Ron stammered.
"WHAT!" Hermione screeched, running out of her wardrobe and going over to Ron. "Goodness! Ron, what exactly happened?"
Ron's eyes narrowed threateningly at Hermione. "He was sitting here. Now he's not."
His friend sighed, exasperated. "What was he do–" Hermione cut herself off as her eyes strayed to her bedside table. "Oh hell! My time turner!"
"Hermione, this is not the time to worry about your enchanted jewelry. Honestly!"
"Ron, you are so bloody daft, my time turner has disappeared, and so has Harry. Please take a moment to use your brain and put it together."
Ron paused briefly, and then his face lit with understanding. "OH! I see. Oh... damn. DAMN!"
Hermione's breath quickened, though she made every effort to slow it. "Oh, Ron, who knows how far Harry went into the past! There's no way for a wizard to go forward in time! Oh my god, Ron, oh my god."
"Hermione, what the hell are we going to do!" Ron practically shouted at her. "My great uncle, Alfred, once tried to travel back in time to the days when his parents went to Hogwarts, and he–"
"RON!" shrieked Hermione. "Ron, that's it! I've read that on occasion, when a wizard unconsciously travels back in time, said wizard gets transported to where they most want to be. Oh my god, Harry might have gone back to see Sirius and James! Oh... and there are side-effects to that risky manner of time travel. He'll be sick and nauseous for a few days, and incapable of rational thought. That's the best case scenario. Worst case, he completely alters the time line, and he never gets born in the first place."
"But..." stuttered Ron. "If he was never born, who would have stopped..." he took a gulp. "V-Voldemort?"
Hermione's eyes welled up with silent tears. "D-don't worry. I might just have a plan..."