"No."
"You're being stubborn."
"No."
The proud, arrogant grin had slipped off George's face entirely. His mouth was set in a deep frown, and his eyes were hard with defiance. He glared at Fred with his arms crossed over his chest.
"George," Fred complained. He set the long, thin cloak on the table and leaned over the back of a nearby chair. "You know it has to be tested on a human."
"No!" George repeated, a bit of panic creasing his determined expression. "Blimey, you really have gone mental."
Fred ran a hand through his hair and let out a frustrated sigh. They had been trying to invent a cloak that could repel an Unforgivable Curse for months, and, after countless nights of sitting in their room at the Burrow late at night and endless research, they had finally invented a prototype. Their only problem was the issue of needing a test subject.
"Look," George said. "You know I could never do that, I'll never do that. I'll hit you with an Imperious if I have to, or we'll conjure a bug or something."
"George, a spider would react a lot differently under the cloak," Fred reasoned. "It's designed for wizards, you idiot. We both know how to ward off the Imperious, what if it works well for us but not for someone who can't? Besides, it's not like I told you to use the Killing Curse."
"You might as ruddy well have!" George spat. "Fred, I could barely stun you in DA without feeling guilty about it."
"The Unforgivables only work well if you mean it, Georgie," Fred pointed out, remembering a book they had taken out of the Restricted Section late at night during their seventh year. "Unless you've been looking for an excuse to knock some sense into me, I doubt the Curse will last long."
George considered this for a moment. He furrowed his brow and stood silently, pacing around the room in deep thought. After a moment, he groaned, pushed his hand through his wild hair as Fred had, and turned back to his brother.
"If I do this, we can't tell anyone. I reckon the shop would be a bit lonely if the Ministry carted me off to Azkaban."
Fred nodded solemnly in agreement. George tossed him the cloak, and he slipped it over his robes, straightened, and braced himself. He stared ahead as George pulled out his wand. Fred could see his brother take a deep breath, his face white. He swallowed heavily as his entire body began to tremble slightly, and looked Fred directly in the eye as he uttered the unspeakable word.
"Crucio."
The pain, though only for a split second, was unimaginable. Fred collapsed to the ground and let out a short scream, internally thankful for the silencing charms placed around the flat. He curled in on himself as his body shook as if hot knives were bursting out of his skin. He wondered vaguely, in the back of his mind, about the strength of the spell, and what the pain would have been like had it been cast by a Death Eater. Then, as soon as it ended, it was over as if it had never happened.
Slowly, he opened his eyes, letting out a short moan, and pushed himself onto his knees. Almost immediately, another pair of hands was gripping him in reassurance, as if they never wanted to let go. He looked up blearily and saw George hovering over him, inches from his face. There were tears running down his cheeks, and he was still paler than the Bloody Baron.
"I'm so sorry," he muttered, grasping Fred under the arms. "Oh, Merlin, Freddie, I am so sorry. I told you I didn't want to do this, I'm sorry…"
Fred grinned weakly as he managed to heave himself to his feet with George's help, stumbling slightly. George put his arm around his shoulders and led him into their shared room, gently lowering him on to his bed.
"I am so sorry," George repeated.
"Georgie," Fred interrupted as his brother took a shaky breath. "I'm okay."
George snorted. "Fred, unless I wiped your memory in the process, I hit you with a Cruciatus Curse. Something tells me you're not okay."
"I'm fine. It only lasted for a second."
"I'm sorry, I'm so sorry." George put his head in his hands.
Fred grabbed the back of his neck and forced it upwards, though gently. He smiled. George hurriedly wiped at his red eyes, wrapping his arms around Fred's neck quickly and squeezing as tightly as he could.
Over the next week, George must have apologized for the Curse millions of times. He finally forgave himself, however, when Fred allowed him to test the next half dozen products on himself and threatened to tie him to a chair when he muttered that he deserved a month in Azkaban.
"Hey, Georgie," Fred said, entering the flat over a week later turning something over in his hands. "I know the cloak was a bit of a bust, but I was thinking we could make a shield for Unforgivables. I made a prototype, and maybe we could…"
George stared at his twin for a moment before he slowly walked over, took the tiny object from Fred's hands, pointed his wand at the thing, and muttered "Reducto."
Fred puffed out his cheeks, though did not protest, as the product blasted into pieces in George's hand. George, seemingly satisfied, grinned at his brother, threw the bits on the floor, thumped Fred on the back, grabbed his sleeve, and marched down to the shop.