Sectumsempra Reversed

His breath was coming out in rasps, his concentration wavering. He really needed to remember to eat, to get some sleep, to exercise—whatever he used to do in his old life. No, he did remember, he just didn't see the point of it anymore.

"Stupefy!"

Leaping behind a toilet stall, Draco narrowly missed the jet of red light. It rebounded off the door, followed by a muttered curse.

"Is that the best you can do, Potter?" he asked, trying to keep his voice steady. Crouching down, he slowly crept towards the other side. "You really are nuts!"

It was just what he had needed: Potter storming into the bathroom, ranting about the Bell girl. Couldn't the high and mighty git for once, just once, leave him be? To realise that the world did not revolve around him?

He needed to get rid of him. Peeking under the stall, he could see Potter's shoes slowly moving around the corner. He raised his wand, his mind running through a list of curses he could use.

Could he kill him? Could he practice what he needed to do, now? On Potter? He'd be a murderer soon anyway, why not take out his biggest enemy? Sure, he'd probably be tossed into Azkaban, but wasn't that safer than here, under his constant watch?

Who was he kidding? Nowhere was safe.

"Reducto!"

Draco cursed as Potter got in first with another spell, missing him by a hair. He hit his elbow against the stall door, the pain shooting up his arm. There was no time to nurse it, however, and he readied himself to attack back.

"I'm not sure why you complain about my handwriting when yours looks like this," Draco said.

His godfather turned around, an eyebrow raised. "My handwriting?"

Draco held up the book he had found and pointed to a scribble on the side of one of the pages. His lips pulled into a smirk as he said, "Either 'Sectumpsempra' is a word you made up or you were attempting to write down an ingredient and failed."

The wizard's dark eyes grew cold, and before Draco knew what was happening, he snatched the book from his grasp. "Where did you get this?"

The blond rolled his eyes. "It was in the pile of Potions books you were supposed to bring to me. Relax, you can take it back; as if I would want something so old and torn. We have more than enough old things around here."

Snape's expression returned to its usual sulky mask, and he put the rugged textbook in his satchel. Then, he turned back to him and folded his arms.

"Your father has given me this week to ensure you are up to date with your skills so you can achieve the Outstanding expected of you. I suggest you pay more attention to what I have to show you than the condition of textbooks. This is advanced work, more than you'll need this year; we wouldn't want you getting burnt or anything now, would we?" Snape said.

Draco scowled, any trace of amusement he had long gone. His father had not missed the news that Granger was top of the class, and as soon as everyone else's holidays had begun, his three-month long tutoring program had begun with Snape at the helm. Potions was one of his favourite subjects, yet not his idea of 'fun.'

Realising that Snape was waiting for him to set up the cauldron for their first concoction, he folded his arms. He would just have to make this fun.

"Brewing the Draught of Living Death is so mundane. Should we not try something a little more interesting?"

"The Draught of Living Death is a basic necessity," Snape replied, selecting a vial of pale yellow liquid from his set.

"I agree that it is useful, but we both know that I will need potions of a different... variety soon."

Snape raised an eyebrow again, picking up some Valerian root. He didn't say no, however, so he pressed on.

"I was thinking you could teach me how to brew that Sectumpsempra potion. After all, you had noted that it was for enemies—at least it looked like that's what you wrote— and we both have plenty of them."

Looking carefully at his godfather, he saw the man stiffen. It was just a small straightening of the back, a pause of his hands as he placed the roots on the workbench, but Draco did not miss it. Curious.

"You will not be needing that."

"Is it not on the curriculum? Don't you think my father would want me to know everything there is?" Draco asked.

His godfather did not look at him, and instead resumed taking out the final ingredients they needed. His voice was quiet when he finally said, "I will be teaching you everything you need to know about potions, not spells. Now, tell me what the first step is?"

Rolling his eyes again, Draco reached for the Wormwood, filing the spell's name to the back of his head. He would have to master it himself one day, but first he would have to show both Snape and his father he was more than capable of brewing potions.

"Sectumsempra!" Draco yelled before Potter could finish his own spell.

He had never had time to practice the spell, but before his eyes, he watched as a white light soared towards Potter. It hit him across the chest, and his heart lifted: it had worked.

The elation didn't last long, though. Lines of crimson crossed Potter's school shirt, and just like ink on a parchment, blood slowly seeped through his shirt. With his mouth open in shock, he fell to the floor.

Draco's head was pounding, the room spinning. It was like he wasn't there, wasn't him who had cast the curse—as though he were viewing the scene from above. He knew he had to do something to stop the bleeding, to stop Potter from convulsing, but his feet would not move.

The bathroom door swung open, and frantic footsteps came running in. Snape bent over Potter's body, his wand moving over it as he muttered some charms. Draco still could not move let alone speak, and when Snape looked up, he knew he didn't have to.

His godfather's eyes were colder than they ever had been, a mix of fear and disappointment hidden in their black depths.

"You will not speak of this," he said, turning back to concentrate on a now unconscious Potter. "Now go."

Draco could only manage a small nod. His godfather had been right that he had not needed that spell, and he sure as Merlin would be listening to him now.

A/N: This story was written as a gift for the lovely Angela (Miss Skinny Love )! Prompt: A reverse!fic where Draco casts Sectumsempra on Harry in the bathroom instead of the other way around—enter Snape… I hope you like this take on the prompt, and thank you for being such a lovely friend! Xx