Disclaimer: Most of this isn't mine. In fact, the majority of it isn't mine.
Wormtail was gasping and moaning with agony. Not until Harry felt Wormtail's anguished breath on his face did he realize that Wormtail was right in front of him.
"B-blood of the enemy ... forcibly taken... you will ... resurrect your foe."
Harry could do nothing to prevent it, he was tied too tightly.... Squinting down, struggling hopelessly at the ropes binding him, he saw the shining silver dagger shaking in Wormtail's remaining hand. He watched the dagger grow closer with dread.
"Wait!" Harry shouted. He was surprised as Wormtail paused momentarily. "I give you this blood." Harry whispered at Wormtail. Wormtail shrugged and the shaking dagger resumed its path to Harry's arm.
Harry felt its point penetrate the crook of his right arm and blood seeping down the sleeve of his torn robes. Wormtail, still panting with pain, fumbled in his pocket for a glass vial and held it to Harry's cut, so that a dribble of blood fell into it.
He staggered back to the cauldron with Harry's blood. He poured it inside. The liquid within, instantly, bubbled up and glowed a sickly green color. With a barely audible "poof" the cauldron imploded and Voldemort's spirit, rose from the ruined mass.
"Wormtail!" Voldemort shouted as Wormtail the rat disappeared among the gravestones.
Wisely, Harry grabbed the portkey and went back to Hogwarts.
A/N: Italics are from Goblet of Fire, pages 642 and 643.
I've always toyed with this idea, just as a what if.. and well, here it is.