Harry sat in the library, studying for an upcoming History of Magic exam that the fifth years would be facing later that week. He frowned when a shadow cut off his source of light. He waited for whomever was standing there to move on, but after a moment he realized  they weren't going to so he looked up. Professor Severus Snape stared down at him.

"You are a parselmouth, correct?" the potions master asked.

Harry blinked. "Um... Yeah?"

"Is that a question or a response, Mister Potter?" Snape snapped.

"Answer."

Severus nodded. "Good. I need you to do me a favor."

Harry's eyebrows shot up. "Favor, sir?"

"Yes. I am prepared to make fitting compensation available to you."

"Um. Okay."

"Good." Severus reached into a pocket of his robe and pulled out an empty vial. He placed it on the table before Harry. "I need this full of snake venom - the species is not important - and I also require several eggs."

"Snake eggs?" Harry asked for clarification.

"No, dragon eggs - of course snake eggs!" Snape hissed. "Can you do this?"

Harry nodded numbly.

"Good. See me after about payment."

The man turned and stalked out of the library. Harry watched him go and then he looked down at the empty vial, the only concrete proof that the last several minutes had actually taken place. The Boy-Who-Lived shook his head in disbelief. He had agreed to do Professor Snape a favor.