While Harry and Ron were off with Mustang, Malfoy was under the oppressive tutelage of Armstrong. Armstrong had, like Mustang, paired off the class and was having them duel. Malfoy was pulled out of a daydream by the big man's voice booming in his ear. It was his turn.
Malfoy looked at his opponent. It was Ginny Weasley, and at his predatory leer she wilted slightly. "This is going to be fun." He checked the fit of his now ubiquitous gauntlets, and the match began. "I tell you what, Weasley, I'll give you a free shot. Hit me." A wall of clay wrapped up his legs. "Okay. My turn." He broke the clay, and clapped his hands. Ginny felt normal at first, then it got hard to breathe, and it started to feel very close, like a pressure building. Very soon she almost couldn't breathe at all, it felt like trying to breathe tar. She began to scream. She felt several sharp snaps in her chest.
"Mister Malfoy, release her! You've won! Release her this instant!" yelled Armstrong.
"Okay." And he did just that. He released the alchemy all at once. And Ginny screamed. The pain she'd felt earlier was nothing compared to this, it was like fire all through her. She contorted herself into a ball and kept screaming until her throat was raw.
"Take her to the Infirmary! Class dismissed!" And Armstrong stormed off to see to his student.
When Ron got back to the dorms, he was sore. Who knew that Gregory Goyle had such a grasp of alchemy? He walked in to find a very distraught-looking Angie Spinnet. "Ron! Oh, Ron, it's," and she trailed off.
"It's what?" He was concerned, because usually Spinnet was rather bubbly.
"It's your sister. She's in the Hospital Wing. Her and Malfoy dueled and he used some sort of alchemy on her. It was like torture when he used it, and it looked like it hurt worse when he released it. She's in a bad way."
Ron didn't remember running to the Infirmary. The next thing he knew he was looking at a bandaged, whimpering form in a bed. Madame Pomfrey walked over. "What happened?"
"As far as I could tell, he used alchemy to increase the air pressure around her to almost lethal levels. It broke two of her ribs. And what's worse, he brought the pressure back to normal all at once. It could have killed her!"
"What could have killed her?"
"A condition that divers call 'The Bends'. When divers dive very deep, the pressure increases around them. Nitrogen builds up in the blood to equalize the pressure. If a diver ascends too rapidly, the nitrogen forms bubbles. If a bubble travels through the blood to the lungs or heart it could kill the person. What Malfoy did was like taking her from the bottom of the sea to the top of Everest in a heartbeat. The worst case of the bends I've ever seen." Ron was furious. He stormed off toward the Great Hall. Revenge would be his.
As Ron made his way down the halls, a piece of his mind was detached from the seething, angry, rest of it. He remembered a book that he'd read, about a detective who'd been in AA. In the book it mentioned a "dry drunk" but what the detective called it seemed to fit Ron's situation. A case of terminal assholeitis. At that moment, Ron dedicated himself to the systematic decontstruction of Draco Malfoy.
Harry and Hermione were in the Great Hall when Ron stormed in. "Where's Malfoy!" He bellowed.
"I don't know, Ron. Why?" asked Harry.
"I'm going to kill that bastard for what he did?" Ron was in a rage, they could see. He was beet red and was on the verge of foaming at the mouth.
"What did he do?" asked Hermione.
"That no-good, lowdown, Mudblood Rat-Bastard nearly killed Ginny!"
"What!" Harry and Hermione were in shock, both at the swearing that Ron was doing, and the fact that Ginny'd had a brush with death. "How?"
"They were dueling in Alchemy. Malfoy used alchemy to increase the air pressure around her until it broke her ribs, then brought the pressure back to normal all at once. The bend nearly killed her."
"So you're going to beat the tar out of him?"
"No, Harry. I'm going to skin him alive and wear his hide for a cloak, tear his greasy head off and use it for a Quaffle!"
"Calm down, Ron. I'm sure there's a less lethal way to deal with this. Ginny's still alive, that's all that matters. We'll deal with this when you calm down and get to thinking straight. Okay?"
"Alright. But I'm going to get my pound of flesh, Harry. That's a promise."
Malfoy, on the other hand, was in the Slytherin Common Room, which had been vacated, scrubbed, and sterilized. He'd realized that when the Weasel found out about his little sister, he might need both hands to keep the red-headed boy off him. So he'd gotten back to Winry and they'd hastily put together an operating room in the Common Room. Malfoy was on the table, biting a piece of leather and trying, unsuccessfully, not to scream. He'd managed to take off his own hand, and was now getting the port for the new hand attached. Winry was cursing and swearing about lack of preparation, unsatisfactory conditions, and a laundry list of other beefs. "This is going to hurt, Malfoy," she said as the port was finished. She took the hand and wrist, and inserted it into the port. Malfoy let out an enearthly howl of agony, and curled up in a fetal position. He blacked out from the pain.
He woke up three hours later on the couch in the Common Room. He looked down at his new hand. It was flat black, and when he flexed his fingers he was overcome with joy.
"Like it?" asked Winry.
"I do."