Will put down the book, his fingertips lingering on the page as his other hand closed around his wand.
"Time to test a few theories."
The next evening, Peter sat bound to a wooden chair in the middle of the Room of Requirement, trembling all over.
"L-Lord Behrens..." Peter's voice was hoarse with fear. "D-did I do something wrong?"
"No, Peter," Will said calmly, pacing around the chair. "I just need you for a little experiment. Don't worry, it won't kill you—at least, I don't intend to let you die."
Peter found that hard to believe. All the research he had brought Will concerned the Killing Curse. Surely that madman wasn't planning to practice it on him?
He decided that if Will tried to use the Killing Curse, he would turn into a rat and escape. These ropes couldn't hold him then.
But Will's next move—and his spell—left Peter dumbfounded. Will drank a bottle of Euphoria Draught, burst out laughing, then aimed a spell at Peter that he never would have expected.
"Expecto Patronum!"
Will had actually cast the Patronus Charm? Peter doubted it could do anything to him, and he relaxed almost completely. He knew what the charm did, and Will probably couldn't cast it successfully anyway.
A cloud of silvery-white light poured from Will's wand tip and enveloped Peter. His mood lifted considerably.
But Peter soon realized something was wrong. What flowed from Will's wand was no longer silvery-white mist, but a thick, almost black haze.
The haze twisted and spread through the air, filling the room as though it were alive. Peter's eyes widened, and a rattling sound rose from his throat—not from fear, but more like an instinctive physical reaction.
The dark gray haze enveloped Peter. Will fixed his gaze on him and watched closely.
Peter