He was fiddling with a cauldron and several ingredients when she entered the room, still foaming slightly.
"Good, there you are," he looked up to see her spitting once again. "Still have some choice words, I see. Well, some of my lessons are harder then others, but I will try to see that you survive them all. Now, come here." She was afraid to say anything and decided that it would be to her benefit to simply comply. "I have everything set up. Here are the instructions," he flicked his wand and a formula appeared scrawled across the blackboard. "If you are successful I have decided to reward you, so be very diligent with your measurements and the order of ingredients."
She found merit to his warning as she soon realized the measurements were very precise and twice caught herself just before adding the wrong item to the cauldron. After what felt like hours she was finally finished with the potion. She examined the pale milky green liquid and wondered what it would do and if green was indeed the correct color. She consoled herself that at least it hadn't exploded like Neville Longbottom's age reversal formula earlier. What a disaster that had been and poor Neville always tried so hard. Just being in the dungeon seemed to rattle the poor boy's nerves with or without Professor Snape present. At least Jessica had been able to regenerate Draco Malfoy's hair without much fuss, not that Draco was likely to let Neville forget the incident. She thought it was best not to share the day's events with the professor since he would attack Neville at any give opportunity, and why make that any easier for him. She sat and watched him work at his desk, waiting for him to notice that she was through. It wouldn't take him long.
"Well, let's see what you have produced." He approached the cauldron and dipping a ladle into it drew out some of the potion. Severus examined the color closely then let the liquid pour slowly back into the cauldron as he surveyed the consistency. "Very good, Miss Jackman. Let it simmer a bit and we will test it shortly." He returned to his desk leaving her to watch the fire. As the flames rose so did her confidence.
"Sir, may I say something?"
"Of course," He laid his quill down and looked up at her. "You have my full attention."
"What gives you the right to strike me? You claim to have my best interest at heart but then you pull something like that and still expect me to trust you? How do you justify yourself?"
He appeared to be thinking hard on the matter. When at last he spoke his silken voice was soft and without a hint of irritation. "Miss Jackman, I have no need to justify my actions. You are my student and you were insubordinate. I have every right to discipline you. That is precisely what I have done. There was no harm done... not really." He held her gaze, realizing that this was certainly not the answer that she was seeking but would be all that he would offer. She seemed to understand this and pushed no farther. A smile tugged at the corners of his mouth, she was learning.
"You find humor in this?"
"I was just thinking how pleased I am with the results of your chastisement. Maybe I should have tried that route sooner."
"What are you talking about?"
"I don't doubt that the shock will wear off, but it is so nice to speak with you while you maintain a civil tongue."
"I have no taste for soap, sir."
"No, neither have I." For several moments he remained quiet, lost in a memory she could not begin to guess at. Suddenly he returned to the present. "Now, let's test that potion out, shall we, Miss Jackman?" He strode up to the cauldron and stirred it once again, before ladling some of the mixture into a small mug. Sniffing it he nodded his approval to her. "I am pleased." He held the mug out to her, "Drink it."
"What? Are you..."
"Manners," he admonished.
"Sorry, sir," she lowered her voice but had trouble keeping her tone even. "But I don't even know what it does."
"Do you think I would poison you?" She did not respond. "I see."
"I meant no disrespect, sir. If you had prepared the potion yourself I would have more faith in it. Maybe I did something wrong."
"You have done exactly what I have instructed, therefore there can be no error. You must trust me." There was that word again. Trust. He pressed the mug into her unwilling hands. "Drink!"
While maintain eye contact with the master, Jessica swirled the potion around then brought the mug up to her lips.
"Wait." She nearly dropped the potion, her heart beating wildly. Was this a test? Had he meant to poison her then changed his mind? Was she being a fool to listen to him talk of trust? What if he hadn't stopped her in time?
He took the mug from her hands and sprinkled some white powder over the surface of the green liquid. "Sugar," he answered the unspoken question. "Doesn't affect the results but it makes it a bit more palatable. Go on now, drink up."
As the thick steaming potion touched her tongue, Jessica was treated to the bitterest taste she had ever encountered. The sugar did little to take the edge off. Much to her chagrin she was unable to stop herself from spitting it out on the floor...and over the professor's shoes.
"Oh my God. I am sorry, Professor Snape," she gasped as she wiped her mouth with the back of her hand trying to dislodge the awful taste. "I didn't mean to..." she stopped. He was leaning back against the table in front of her with he arms across his chest and a very satisfied look of his face.
"You have done very well indeed."
What had she done well? Jessica looked at him in confusion. The only thing she could tell was that she had spat on him and seriously doubted that this would bring his complement.
"Don't move." He retrieved a small mirror from his desk and carried it toward her. "Look here." She found it strange that he held the mirror slightly to her left but leaned towards it peering at the silvery surface. This couldn't be.
"I don't see anything, sir."
"That is as it should be. I am impressed that you have brewed this potion correctly on your first try. You have a steady hand and a keen eye for potion making."
"An invisibility potion?"
"Yes, of my own design."
"But there are magical items, charms..."
"That are all fallible. Counterspells can render any other means of invisibility useless. Even simple daily occurrences can negate conventional means, but my potion can not be countered." He heard her scoff. "You are completely undetectable. Wait. A demonstration... don't move," the intensity of his tone froze her to the spot. With a flick of his wrist the floor surrounding them was covered in a fine layer of sugar.
"I sure hope he doesn't expect me to clean that up," she mumbled. Another wave of his wand and he disappeared.
"Now pay attention." He walked toward the cauldron leaving a trail of footprints in the dust. "Not exactly fool proof, is it?" He negated the charm and reappeared. "Your turn. Come to me." She obeyed and went to stand beside him. "Notice any difference?" Looking around, Jessica saw that she left no tracks on the floor. "Completely impervious to charms, detectors, even Moody's roving eye."
"This is amazing, professor." He spun around following the sound of her voice. "Is this how you get near the Dark Lord?"
"That is none of your concern and stop moving about." He heard her giggle as she moved just out of his reach. "You are acting like a child," his voice was controlled but she heard his threat clearly and stood next to him.
"I am here, to your right."
"Thank you. Now there is another property to this potion that can be quite useful." He took a sip from the mug and his eyes fell on hers. She moved slightly and his gaze followed. He could see her. "Yes, now you understand it's true potential, don't you? A group of people able to communicate silently amongst themselves while invisible to the world around them."
"Incredible. How long does it last?"
"That would depend on how much you ingest. By the condition of my shoe I should think that you will be visible shortly."
The dungeon door creaked open and Hagrid's shaggy head peered into the room. "Professor Snape? Are you in here?" Snape held her eye and placed a finger against his lips. "Guess not," Hagrid murmured as he surveyed the room and the dusted floor. "Blimey, what a bloody mess. Best let the house elves know," and with a click of the bolt he was gone.
"Do you do that often?"
"From time to time. Makes it so much easier to catch students up to no good. I can always find a reason to deduct house points or hand out detentions. Comes in handy when I am low on supplies and need someone to pluck brains or eyes for me."
She noticed that he was no longer looking at her. "Are you visible?"
"I am." She could feel warmth spreading through her body. "And now so are you," he smirked. "Let's get this cleaned up before the house elves give me hell." With a wave of his wand the floor and cauldron were immaculate. "Let's see, I believe I made mention of a reward. Follow me."