"What are you doing here, Potter?" every syllable in his voice filled with hatred.

"Uhhh...I uhm-"

"For once the fabulous Potter has no words to say. How strange." he muttered, hands in his robe pocket-the one with his wand.

"I...uhh... needed a book you checked out," James said.

Snape's eyebrows furrowed and his expression darkened more, if that was even possible.

"What book?" he asked suspiciously. "And for what purpose?"

"Why do you care?"

"Why are you in the Slytherin Common Room without permission? Why are you creating unsupervised potions?"
James gulped.

"I know what you've been doing, Potter. I hear that loud-mouth Siruis talk about your 'master plan' and I'm quite tempted to tell."

"Then why haven't you?" James challenged.

"I had to be sure that it was true, but you want my book, so it must be. Sectumsempra!"

A deep gash appeared on James cheek.

"The bloody hell is wrong with you?" James said, crawling back and sitting on the apparently unnoticed cloak and book.

"You! Sectumsempra! Sectumsempra! Sectumsempra! Sectumsempra!" Several deep gashes appeared in James' hands as he attempted to get his wand.

"Stop it! What's wrong with you?" he yelled.

"Sectumsempra! Incendio! Sectumsempra! Sectumsempra!" he said madly. They always say that the 'bad guy' would have an evil glint in their eyes, but Severus had nothing. Just empty blackness, not a spec of light.

James also had the uneasy feeling that maybe Snape wasn't the bad guy...but there was no denying that James was probably going to die. He had a slight burn and tons of horrendous gashes. He was cowering like a baby, his pain and blood-loss too much. He almost cried.

Then the door opened and a Slytherin girl walked in.

"Oh my god. Severus! What are- You're going to kill him, you freak!"

James took that opportunity to slip the cloak and book into his robe and trudge away, his balance failing more than once.
Why had Severus been so angry? Because he had overheard James saying that the potion would be how he'd win Lily over? Was it just pure hate?
James didn't know, but as he neared his room, he realized he liked being alive. It worried him that he had this thought this because it meant he had felt his life was at threat: people usually appreciate what they feel they're going to lose. He knew that if not for the girl's convenient entrance, he would have surely died.