Under much protest, Lily was confined to her dorm for the following week. James spent as much time as humanly possible plotting ways to sneak in and see her, and the rest of it wandering around coughing and looking miserable.

The next weekend, Sev was sitting in the Prefects' Common Room reading when the two of them came in. James was fussing over his girlfriend like a mother hen.

"I still say you shouldn't be up," he objected.

"Did I not tell you I was better?" Lily growled at him. She looked it, too, although not totally. She was still pale, but less like one of the walking dead. The bed rest had obviously agreed with her.

"Okay." James pulled a face. "We can stay here a little while if you really want, but then I wanna take you off to bed."

That seemed like a good cue to announce his presence. Sev allowed himself to snort and said "I think we already knew that, Potter."

James whipped around, face flaming, but Lily giggled. "Lily," he whined, dismayed by this traitorous response.

"Sorry," she said, still giggling. "But you totally asked for that."

James scowled at Sev, bright red with embarrassment. "Keep your mouth shut, Snape," he advised.

"I think you'd be better off taking your own advice," he said pointedly.

Behind him, Lily was shaking. For a moment, Sev thought she was still laughing, but then he realised something was wrong. "Potter, you might want to stop glaring at me and pay some attention to your girlfriend," he advised.

James frowned, but turned and ran to Lily's side when he saw the way she was shaking. "Lily! God, Lily, what's wrong?" She was shuddering more and more violently now, as if she was having a convulsion.

He grabbed for her, but she shook out of his grasp and collapsed to the floor, convulsing wildly now. Sev's mind abruptly flew back a few years to when he'd last seen a similar fit. Suddenly, he knew exactly what was making Lily ill, and how it had been administered.

James, though, didn't have the slightest clue, and was looking extremely terrified. "Lily!" He gripped her by the shoulders, completely unsure of what to do. He looked up and his eyes met Sev's.

"Help me!" he said desperately. If he even remembered that Snape was his deadly enemy, the importance of that was lost in his fear and confusion. "Please, I, I don't know what to do!"

Sev made a split-second decision, which might or might not have involved a careful weight up of the pros and cons of acting. He hopped out of his chair and knelt down beside the spasming Lily, helping the other boy support her.

"Hold her up; we don't want her to swallow her tongue or anything," he ordered. "And give her some room to breathe!" He pulled open her outer cloak, not entirely coincidentally yanking off the Prefect badge that held it in place.

"What's happening to her?" demanded James fearfully.

"It's some kind of seizure. It should pass in a minute, she'll be okay as long as she can breathe properly." It wasn't medical knowledge that made him so sure of that, but James didn't need to know how he knew it.

Despite the fact that he and Snape had long been enemies, it didn't seem to occur to James to doubt his word. The ability to keep a completely calm voice in times of crisis could work wonders.

Sure enough, Lily's convulsions began to subside, and abruptly she sucked in a shuddering breath. "Lily!" The world of relief in James's voice was clearly audible.

"James." She blinked blearily, and frowned up at the other boy. "Severus?" Either she was genuinely surprised to have him come to her rescue, or she'd retained the presence of mind to act that way.

"Um..." James wasn't sure what to say, suddenly remembering himself but not being unreasonable enough to abruptly snap at Sev after the way he'd helped. Sev solved part of his problem by quickly letting go of Lily and standing up.

He made a big show of opening the hand which held the Prefect badge, and grimacing at the red stains all across his hand. "What's wrong with these stupid things?" he demanded loudly.

Fortunately, James wasn't particularly slow. His eyes suddenly widened behind his glasses, and he wrenched his own badge off. "The badges! They're poisoned!"

Sev allowed the badge to drop from his fingers, but his cover required him to scowl and say "Who'd care enough to poison you?"

James hesitated, natural instinct to pin it on the Slytherins somewhat muted by current events. Luckily, Lily was on the ball. "Death Eaters," she said loudly. "Should've known they wouldn't go for a mudblood Prefect." She coughed, still looking dangerously pale.

"Lily!" James sounded shocked.

"It's only a word, James. It can't hurt me," she reminded him sharply.

"Unlike this stuff," he said, looking down at the two badges where they lay on the floor. He turned his gaze back to Lily, and looked deeply concerned. "You took it off; you'll be okay now, right?" He seemed to have completely forgotten that he himself had been exposed in his worry over Lily.

Sev figured it fit his persona to be scathing about James's short-sightedness. "It's poison, Potter, you've already got it in your system. All that means now is that you won't get a stronger dose."

James's hands balled into automatic fists, and then he paused. "Yeah? Well then, you fix it."

Sev frowned at him. "You what, Potter?"

"You fix it! You're the Potions genius - make me an antidote!"

James had managed to provide him with a rather neat way out of this, but he had to protest anyway. "Why the hell should I?"

James nodded to Sev's red-stained hand. "Because, in case you've forgotten, you got poisoned too."

Actually, Sev was just a hairsbreadth away from certain that he was in no danger, but James didn't know that. He compressed his lips into a tight line, and said sharply "Then we'd better do something about it, hadn't we?"

Sev would have been amused at the symmetry if it hadn't been a bad time to let his inner smirk show. Here he was again in the exact same Potions lab he'd first tutored Lily four years ago. Here he was, helping his supposed deadly enemies. Forced into it or not, that wasn't likely to wash well with Malfoy - so it was just as well he'd cottoned onto something that would excuse his actions.

The second Lily had gone into convulsions, he had thought of Erica Swift; an older student who had fallen afoul of a nasty little concoction of Malfoy's. It was a kind of poison that only affected mudbloods - and it came in the form of a blood-red powder. The second he had remembered that, it had all made sense.

Or nearly all. This little trap had been devised purely for Lily; he was guessing they'd poisoned both badges simply because there was no way of telling which would be hers. The plan must have been to trickle the poison into her system slowly enough that the progression looked like a natural illness. Insofar as it had gone, it had worked.

But... James had become ill. Only over this last week or so, and not very severely... but he had definitely become ill.

James Potter might be the antithesis of your average Death Eater in nearly all respects, but there was one way in which they were perfectly matched. The Potter family were pureblood all the way; uncounted generations of wizards and witches stretching back through the ages. Malfoy's perfectly self-contained little poison had mutated.

Whether James had become ill through the persistent trickle of poison into his system or through close contact with Lily was open to debate, but either way it spelt serious trouble. If the Death Eaters had drawn up schemes to unleash their weapon on the world, they could forget it. If it could mutate once, it could do it again, and all of a sudden the purebloods might find themselves in as much danger as their enemy.

With all that in mind; well, naturally he had to follow James's orders and develop an antidote.

Any other student, indeed any qualified wizard who hadn't made a specific study of Potions, might be totally stumped. But Sev had read every available text on the subject, he'd had experience developing potions without using a set recipe, and he had somewhere deep down an instinctive grasp of the subject. With part-memory, part-instinct, he easily pulled ingredients together and mixed them however it felt right. The first attempt didn't satisfy him, nor the second, but when he poured a drop of his third potion on his stained hand, the redness turned clear with an audible hiss.

He turned to the impatiently pacing James. "It's done."

James eyed the blue liquid suspiciously. "That's your antidote? It sounded like acid!"

Sev proffered his now stain-free hand. "Does this look burned to you?"

"Yeah, but that's hardly the same as drinking it." James hadn't been at all happy when Sev had brusquely informed him that if he wanted to get read of a poison inside him, he was going to have to drink the antidote.

Sev sat back with his most indifferent shrug. "Trust me. Don't. See if I care."

James looked at the potion with distaste. Then, with a concerned expression, he looked across at Lily. She'd made an effort at seeming her usual self on the walk over to the Potions lab, but Sev's experiments had taken time, and that had sapped her strength. She was leaning on the worktop, a tiny distance away from falling into a deep sleep.

James stared at her for a long moment. Then he turned to Snape, and ordered "Give me some of that. I'll drink it first."

"Whatever." Sev poured some out into a beaker and handed it to him. "Knock yourself out."

James regarded the blue antidote with some trepidation. Then he grimaced, and downed it in one gulp. Immediately, he cried out in disgust. "Ugh! God, what's in that?"

Sev shrugged again. "You want sugar, go to Honeydukes. I'm not here to make your life easier." Truth to tell, it would have been simplicity itself to tweak a few things and make the potion more palatable, but that had hardly seemed the sensible thing to do.

James looked ready to murder him, but instead he forced himself to take a deep breath. Then he paused, looking almost comically surprised, and took another. "Hey, I'm not coughing! I think I'm cured."

"Oh, happy day," said Snape, completely expressionlessly. James scowled at him, but he couldn't hold it for long in the face of his relief. He dashed over to the cooling cauldron and scooped out another dose.

"Lil. Come on Lily, drink this for me." She groaned at having to raise her head, but he slipped and arm around her shoulders and managed to get her to drink it. She smacked her lips, and grimaced.

"Ack, that's foul."

"Oh yeah." But James was grinning at her. "How'd you feel?"

"Better," she said, sounding as surprised as he had. The change flowing through her could almost be followed by eye. Her milk-white skin began to redden up to a more natural colour, and the brightness in her eyes returned. "Actually, I feel great."

James made a cry of delight, and impulsively kissed her on the cheek. Lily blushed and pushed him off. "Stop that." She looked up at Snape and ordered "Quiet, you," at one glance at his expression.

James, however, refused to be downhearted. He hugged Lily against him, and said "God, you scared the hell out of me! I'm so glad, I could, I could- I could almost hug Snape!"

"And I could drop-kick you through those double doors over there," Sev told him warningly.

"I said almost," he said, grinning. He hesitated, and then got up and went over to their unlikely saviour. "I know you can't stand me and hell, I don't like you very much either, but... thank you." He held out a hand for Sev to shake.

Sev just looked at him until he dropped it. "Potter, you'd be ill-advised to take this as evidence I give half a knut whether you live or die."

James scowled at him, then shrugged and grinned. "Whatever, man." He turned around, and walked out. Lily trailed after him, pausing only to silently mouth 'liar' at Snape. He gave her his best Malfoy sneer in reply.

When they were gone, Sev quickly poured the rest of his antidote into a couple of potion bottles and stopped them up. He would have to give a sample to Malfoy to pass on to his contacts, and it seemed like a good idea to keep some for himself. Then he set to clearing up the Potions lab.

It wouldn't matter if Professor Ephemeria caught him in there alone; he was often up to extra-curricular experiments. The danger had been if he'd been seen working for his supposed deadliest enemies.

He had to trust that Lily would convince James not to tell anyone of his involvement. That should hold true for their fellow students - James would hardly like to admit to being indebted to Snape - but no doubt the two Gryffindors would report the poisoning attempt in full to someone on the staff. Which made it almost certain it would get back to the Death Eaters.

He knew he could talk himself out of trouble, especially with the knowledge that the hex had jumped to a pureblood wizard, but it would hardly endear him any further to Malfoy.

Malfoy would take blind dislike over logic any day - after all, that was practically a required qualification for becoming a Death Eater. Despite the fact that Sev's actions had been the only ones possible to keep his 'loyalties' a secret and prevent a mass epidemic overtaking mudblood and pureblood alike, Malfoy would focus on him having become 'some kind of Muggle-lover'.

What little trust Sev had won himself was rapidly going down the pan. Malfoy already blamed him irrationally for the failure of last year's Death Eater raid, as if by staying as a rearguard himself he might have ensured better success. Actually, that was probably true, but only because Sev had secretly masterminded the resistance. He was a pro at playing both sides against the middle, and whilst this new twist made things far more complicated, he could wriggle his way around it.

It wasn't Malfoy he was worried about, nor even the staff Death Eater. It was doubtless the latter who had masterminded this little scam, since Malfoy couldn't have got access to the badges, or laid a suitable enchantment to keep the poison flowing. That unknown staff member would doubtless be extremely annoyed, and might keep a closer eye on Sev - but he always behaved as if he was being watched in any case.

No, this little escapade had earned him something far more dangerous than Malfoy's spite or the Death Eater's scrutiny... James Potter's reluctant gratitude. If he wanted the world to keep believing the personality he projected, he was going to have to do something about that... and fast.