Yo! Thank you to all readers so far!

Severus was at home, hunched over the workbench in his potions lab, his brow creased in frustration. It had been three days since he'd left Potter in the Dark Lord's foyer and returned home to begin identifying the potion Dumbledore had given to Granger.

But he was failing.

He went through his mental catalogues, trying to recall not only every potion that was light green in colour but also every potion that would be light green if it were brewed incorrectly. He knew a fair number of potions that would or could be this colour, but he recognized all of them by scent.

Severus didn't know the scent of this one.

He knew many by touch and taste as well, but he couldn't risk touching or tasting the potion when he didn't know how safe it was. Unlikely though it was, there was a chance for this to be a poison, and depending on how strong it was, even the slightest touch or taste could go poorly.

Where had Dumbledore obtained this? Severus was the one who typically prepared any potions or salves the Order needed, even creating new ones occasionally. But he hadn't brewed this, and nor had Dumbledore mentioned requiring any potions save for Lupin's wolfsbane. First he hadn't been told about Potter's Order guard being removed, and now this?

How little did Dumbledore trust him?

Severus had become a spy at Dumbledore's behest, and now the blasted old man couldn't even be bothered to put a little trust in him? Did he suspect that Severus' loyalties really did lie with the Dark Lord? It was going to be a problem if he did. For many reasons.

What else did he know about this potion? Hadn't Granger said something? Yes, she'd said it was to be added to anything Potter drank aside from milk. So, what did that tell him?

If Dumbledore had specified that it had to be added to a drink, did that mean it wouldn't be effective if it was added to food or taken on its own? And what about milk? Would it have the same effect where it simply wouldn't work? Or would it cause an entirely different reaction?

This, he could test.

Leaving his lab, Severus gathered various foods and drinks before returning to the lab and setting everything out across a clean workbench.

With only a small quantity of potion to work with, he was going to have to be careful with his tests. He didn't know whether Dumbledore would give Granger another vial to dose Potter again, or if this was a potion where a single dose would be enough to work.

Severus put a single drop of the potion onto a biscuit, some chicken, a bowl of soup, and a slice of apple, but there were no visible changes. He detected no change in scent either. That meant little, of course. If Granger was to use the entire vial at once, then it was unlikely that one little drop would have much of an effect.

Moving on to liquids, he added a drop into a glass of water, pumpkin juice, tea, coffee, and milk. Like with the food, there were no changes in the way the liquids looked or smelled, with one exception.

The milk.

The instant the potion touched its surface, the milk began to bubble as if it were boiling. That was when he caught the scent. It was so subtle he barely noticed it, but it was definitely there. Tree bark.

Severus' eyes narrowed. Tree bark? There were potions out there that used tree bark, but not many, which he'd always thought was surprising, considering how versatile it could be as an ingredient, especially with how many different trees there were.

Did he know of any potions that had tree bark in them and reacted oddly with milk?

There were two he could think of off the top of his head, but neither of them was green. One was a very dark purple while the other was a murky brown. Even when brewed incorrectly neither potion would be any shade of green.

Frowning, he left everything under a stasis charm and headed to his study where he started pulling books off of shelves. Severus knew a good deal about potions, and he certainly was an expert, but that didn't mean he knew everything. There was a chance he was forgetting about an obscure potion, or maybe there was a new one he hadn't gotten up to date with yet.

He would go through some books first, and then go over how most ingredients reacted when they came into contact with milk. It was frustrating that he had to go back to the basics, but at this point, it was the only thing he could do aside from touching or tasting the unknown potion himself.

Severus' research did turn out to be fruitful, giving him a few ideas for what the potion could be, though he wasn't able to find anything exact. Whatever it was, it hadn't been published in any book or journal, which told him that it was most likely something either new or unregistered.

Returning to his lab, Severus began to brew, attempting to make something the same colour, scent, and consistency. The majority of his batches came out as failures, but there were a few that matched well enough. He then further tested these by adding them to milk, looking for the same reaction the original potion had, but was again met with more failure...

Days later, he finally managed to brew a potion that was the same light green colour and consistency as the original potion. Adding it to milk resulted in the milk bubbling and giving off a faint scent of tree bark, just like Dumbledore's potion. Severus couldn't say that he had succeeded in recreating it, but this was certainly the closest he'd gotten.

The potion he'd made wasn't poison, so he decided to drink it to see what it would do. A dangerous choice, to be sure, but a necessary one.

He drank only a very small amount of the potion and unbeknownst to himself, ended up spending the next few hours slumped over the workbench in a stupor, his mind uncharacteristically blank.

When he came out of the stupor, he didn't remember much of anything and realized what he really needed to do was administer the potion to someone else while he supervised. It was the only way for him to find out the potion's purpose.

It wasn't going to be safe, exactly, but it was the only option he had left. And in any case, he appeared to be alive and well despite drinking the thing, so it was probably going to be alright.

Probably.

He couldn't test it on the Dark Lord, nor did he want the Dark Lord testing it on him. Of course, he couldn't use it on Potter either. Lucius was an option, but then he would owe him a favour and Lucius would, no doubt, drag him off to some irritating gathering or another and Severus had no desire to go through that right now.

He figured Lupin would have no problem aiding him if Severus told him it involved Potter's safety, but not every potion worked well with lycanthropes, and even if this one did, the full moon was approaching and Lupin was taking the wolfsbane, which couldn't be mixed with other potions.

Ah, but there was one other person he could ask, wasn't there? A young but sensible man who already knew at least a little regarding Potter's situation. Yes, Bill Weasley would do.

"So, what's this about, Professor Snape?" Weasley asked as he glanced around Severus' lab curiously.

Hoping Weasley understood the gravity of the situation, and he was sure he did, considering Severus would never let anyone, let alone a former student, into his house, he nodded at the closest workbench.

"Someone was asked by Dumbledore to dose Potter with a potion," he explained, "but fortunately for us, Potter found out about it and was able to obtain the potion."

Weasley frowned. "What's the potion for?"

"That is the problem," said Severus. "I don't know. I don't know what the potion is and have spent the past few days attempting to recreate it. I believe I have succeeded, but..." He explained what happened when he'd drank the potion himself.

Weasley crossed his arms, his frown deepening. "Right. I guess that makes sense. So, you want me to drink it so you can see what it does?"

"Yes."

"It is safe, right?"

Severus smiled wryly. "I'm still standing, no?"

"...Fair enough. Well, if it'll keep Harry safe, then I guess that's fine. You're saying it isn't poison, and I believe you."

"I appreciate this, Weasley," said Severus, pouring the potion he'd prepared into a glass of water.

"Never thought I hear you say that."

"Don't push it, Weasley."

With a laugh, Weasley accepted the glass and after taking a breath, downed the water. Severus took the glass from him and set it down on the workbench, dark eyes locked on the man before him.

"How do you feel?" he asked.

"Light?" Weasley offered. He looked at his hands. "Kind of...floaty. Like I'm on a broom."

"You're still coherent."

"Prob-probably not for long," Weasley admitted, hands falling to his sides. "It's-it's getting hard to-to think."

"Hard in what way?"

"Can't fo-focus."

Weasley's eyes were starting to glaze over, Severus noted. It seemed like it wasn't only his mind that was struggling to focus. He was still standing, and it didn't seem like the colour of his face had changed. Other than the unfocused eyes, Severus couldn't see any change.

"Weasley?" Severus received no answer. "Weasley? Bill?" But still nothing. Reaching out, he checked Weasley's pulse, finding it slower than what he considered normal but still steady. "Sit down, Weasley." And to Severus' surprise, Weasley obeyed, walking the three steps to the closest wooden stool which he perched himself on without a word.

"Weasley?"

"Yes, Professor Snape?"

A little surprised by the response, Severus hesitated slightly before asking, "How are you feeling now?"

"Oh, I feel fine, Sir."

He was saying that, but Severus saw that Weasley's eyes still didn't look quite right. He appeared perfectly normal aside from that, but even then, Severus felt a sudden sense of dread. He was starting to get the feeling he knew what this potion did.

"Fetch me a jar of lacewing flies from the store cupboard there, Weasley."

"Sure." Without complaint, Weasley got up from the stool and crossed the room to his store cupboard where he quickly found the correct jar and brought it back across the room. "Here you go."

Severus took the jar, mouth dry. He asked Weasley to do a few more things and asked him some questions as well, and Weasley obeyed him cheerfully. Yes, he definitely knew what the potion did now.

Which meant...but no, he was jumping to conclusions. This was the potion he'd brewed himself. He wasn't positive it was exactly the same as the one Dumbledore had given Granger.

When the potion wore off, he kept Weasley nearby for a few hours to watch for any side effects, and two days later, brought him back to test the original potion. The response was exactly the same. Severus had, in fact, successfully recreated the potion.

After telling Weasley not to tell a soul, least of all Dumbledore, Severus saw him off and then slumped against the door. How was he going to explain this to Potter and the Dark Lord?

That's it for now. Looking forward to reviews! Laterz!