It was James Potter. He stood in the doorway still in his sleep-gear, eyes wide behind his glasses and hair even more ruffled than usual. "Hey! What did you do to her?"
Fennel rolled his eyes in disbelief. "Oh, good God, another one." He raised his wand to fire off a curse, but James was quicker on the offensive than Lily.
The spell was not strong enough to overcome a master wizard like Fennel, but it was enough to make him briefly fumble with his wand. James, foolishly, chose to rush to Lily's side instead of try another spell.
"Lily! Are you okay?"
Sev could have told him not to waste his breath; the Stun spell would last a long time if it wasn't magically lifted. Realising she couldn't hear him, James twisted around, but Fennel was already pointing his wand triumphantly. "Care to try your luck, Mr. Potter?"
Unnoticed, Sev stepped out of the shadows behind the pair of them. His shadow-spell was falling away quickly, but he had a cure for that. Ducking over to Fennel's discarded invisibility cloak, he tugged it over his head.
Unbelievably, James was actually raising his wand for another spell. But even his lightning reflexes weren't enough this time. "Stupefy!" He slumped to the ground beside Lily.
Fennel shook his head, and moved over to the door to check no one had heard them. Audley Fletcher, amazingly, hadn't even stirred. Sev couldn't tell if he was charmed to keep him from waking, or just an incredibly heavy sleeper.
He'd hoped, when James had showed up, that this could have been fixed without him having to tip his hand. He should have known better than to rely on somebody else. Now he'd have to reveal himself - unless...
He looked across the room for a likely object. Ah! Under the cloak, he pointed his wand arm and whispered "Accio beaker!" The empty glass beaker on a table by the wall leapt into the air and sped towards him.
Before it could complete its journey, he reversed the Summoning Charm with a Banishing Spell. Caught between two conflicting spells, the beaker came to its own conclusions - and fell to the ground in an explosion of glass.
Fennel jumped as if he'd been cursed, and whipped round. "Who's there?" he demanded furiously. "Peeves? If that's you-"
Had Sev not been busy, he would have stopped to consider the ridiculousness of Fennel shouting at the obnoxious poltergeist for interrupting his murder plot. However, unlike James Potter, he knew when to take advantage of a distraction.
Still invisible, he glided over to the unconscious Lily and touched the end of his wand against her shoulder. "Enervate! he whispered, whilst Fennel was still staring round the room in furious anxiety.
Lily pushed painfully to her feet, and made as if to speak; Sev stepped directly behind her and covered her mouth. She struggled, but he whispered directly against her ear "It's me." She stopped trying to fight him, and allowed him to pull her down to the ground again where she wouldn't be seen.
"I'll wake James," he whispered. "Keep him quiet. Use the Stun charm on Fennel - both of you, together, and I'll do the same."
She nodded in mute understanding, and Sev dropped to his knees beside James. "Enervate," he muttered, and then he quickly ducked out of the way before he could be aware there was an invisible person lurking over him.
Lily, he was gratified to see, performed perfectly. She gagged James as Sev had done her, and communicated in sign language the plan. Then she did a three-two-one count, holding her hand up so that Sev could also see.
Fennel, finally satisfied and turning back towards the sleeping Audley, never knew what hit him.
And in that roared command, who was to say if there were two voices or three?
"Get Dumbledore," James urged Lily, going over to stare down at the unconscious Potions master. As she ran out of the door, Sev in his invisibility cloak brushed close by her ear.
"Don't tell anyone I was here," he asked her quietly.
Still wearing the cloak, Sev watched events unfold from the sidelines. Dumbledore and half the senior staff came charging up the corridor, and Fennel was carried away to the dungeons by Hagrid.
James and Lily were fussed over, hugged, and inspected for injuries by every single person in the room. Sev was extremely glad to be out of it.
It was only about twenty minutes later that anybody actually thought to wake Audley Fletcher. He sat up with a stretch and a yawn, and said blankly "Why is everybody in the infirmary?"
The two young heroes were taken into Dumbledore's office, where they sat sipping hot chocolate and were bombarded with questions. Their head of house, Professor Vitae, couldn't seem to stop giving them comforting hugs; Lily didn't seem to mind, but James was looking decidedly embarrassed. Professor Fractalis was stuttering incoherently, and only Dumbledore and Malachite seemed calm.
"Tell us again what happened, Lily," Dumbledore urged.
Lily had given no word to Sev that she would do as he asked, but she did anyway. She told the truth, but not all of it; carefully editing out Sev's involvement. "I just... at the Quidditch match, I was watching Professor Fennel. I thought, it seemed to me that he tried to poison Audley! I mean, he fell off his broom and everything, and we all know he's never done that. It was just something in his expression... and then Audley sicked it up, and he seemed so furious..."
"So you were worried about Audley, and you went to check on him in the middle of the night?" said Dumbledore gently.
Lily nodded emphatically. "I hid under the covers, and Professor Fennel came in, and he had his wand out ready to use a curse. I didn't know what else to do, so I just jumped out and tried to stop him, and he Stunned me." She frowned prettily. "And I guess that's when James arrived."
"Ah yes, Mr. Potter. Pray tell us why you were roaming the corridors late at night? On a similar mission of mercy?" said Malachite dryly. James and Sirius' mischievous exploits were already somewhat infamous.
"I was... I was..." For some reason, James glanced over at Dumbledore for reassurance. "I was going to check on somebody." Malachite opened his mouth to query him, but the headmaster waved him quiet.
"I know what this is about. Tell your story, James."
As James launched into a rambling explanation of how he'd heard a commotion in the infirmary and gone to investigate, Sev filed away the odd reaction thoughtfully. James Potter was up to something in the middle of the night that the headmaster knew about. Interesting...
"-and so I tried to use the Disarmament Charm, but it didn't really work, and he Stunned me, too. But I guess the Stun must have been wearing off of Lily, and then she woke me up and we both cursed Fennel at the same time."
Dumbledore nodded slowly, digesting that. "And there was nobody else involved?" he asked, with sudden sharpness.
"Nobody," said James confidently. Lily didn't answer, and Dumbledore gave one of his unreadable half-smiles. Snape would swear that, just for a second, his eyes flickered over to where Sev was hiding under the invisibility cloak.
Professor Vitae hustled the two Gryffindors back to their respective dorms, still fussing over them loudly. Malachite lingered a moment, sipping his mug of chocolate thoughtfully. "What was that with the Potter boy?" he asked, arching one fine brow.
Dumbledore smiled mysteriously. "Nothing you need to concern yourself with, Carnus."
"Ah, but I am concerned," said the Defence Against the Dark Arts master. "You're too lenient sometimes, Albus. Let the children have their fun, by all means, but don't let them run riot."
"I hardly call foiling a murder plot 'running riot', Carnus," Dumbledore pointed out lightly.
"Yes." Malachite looked thoughtful. "Poor, deluded old Fennel. What do you suppose he thought he was doing?"
"I find, when it comes to matters of murder, that looking for logical answers seldom works," said the headmaster pensively.
"Yes." Malachite sighed. "Well, they'll get nothing out of him once the Dementors get hold of him."
"Dementors?" Dumbledore looked angry.
"The boy's father's an Auror, Albus," he pointed out. "He'll be furious - they'll drag Fennel off to Azkaban before you can blink, and what's left of him won't be much use to anybody."
"Fools," said the headmaster, in a dark tone Sev had never heard from him before. "The Ministry refuses to listen to the evidence that mounts before it. This is an evil time, Carnus. The darkness is ascending."
"Shadows, Albus," said Malachite reassuringly. "It's just shadows. It'll all come to nothing in the end."
"Perhaps," said Dumbledore, pushing around a few marshmallows on a plate. "Perhaps." But as Sev snuck out of the office on Malachite's heels, the headmaster's troubled expression stayed with him.
It was only a handful of weeks from the end of term, and the remaining potions lessons were cancelled - to everyone's delight.
Lily and James were lauded as heroes. Everyone crowded around them, demanding to know the exact details of everything that had happened that night. Most of the students were almost indecently gleeful that their hated Potions master had turned out to be a would-be-murderer.
For a while Audley Fletcher was happy basking in the glory of being the intended victim, but fairly soon he was telling an all-new version of the story where he heroically faced down a rabid Fennel, and James and Lily were relegated to supporting characters only.
Content to be very firmly out of the limelight, Sev stuck with the Slytherins. None of them were half so thrilled as the rest of the school at how things had turned out. Malfoy was disgusted at the idea of James Potter playing the hero, and was heard to mutter in the secrecy of the dorm how it would have been better for all of them if Fennel had succeeded. After listening to Fletcher going on about his own brilliance, it was worryingly difficult to disagree.
Sev kept the invisibility cloak, hiding it away in a secret compartment even Malfoy didn't know he had. He had a feeling this thing with Fennel was only the tip of the iceberg, and being able to sneak around unseen could be very useful in the near future...
He avoided Lily for as long as possible, but eventually she managed to throw off her crowd of admirers and gawkers to corner him in a corridor.
"You. Come with me." She dragged him off to a quiet corner of the dungeons. With the potions lessons all cancelled, nobody wanted to go down there. The dungeons were dark and dank at the best of times, and in summer most of the students found them unbearable. Sev, personally, rather liked them. He did most of his best thinking in the dark.
"Okay. It's time to tell me what you're playing at," Lily demanded.
"I don't know what you mean," he said lightly.
"You always know what I mean," she said, with a pointed look. And how could he argue? "I did what you asked!" she exploded. "I kept secret about your part in this. I had to lie to a lot of my friends! So the least you can do is tell me why."
"I would have thought that was obvious," he said quietly. His soft, cool tone was a marked counterpoint to her impassioned ranting. "For the same reason I kept quiet all along. I'm the observer, Lily. I have to remain on the sidelines, if I'm ever to see anything at all."
"There's a difference between 'on the sidelines' and 'on the other side'!" she shouted. "They all hate you, Sev! They all hate you because you're one of the 'evil Slytherins', and I want to tell them all how completely wrong they are about you and you won't let me!"
Sev remained impassive. "I can live with their enmity, Lily."
She scowled, looking just about ready to spit. "If you only told them-"
"You can't tell them, Lily," he insisted firmly.
She shook her head at him. "This is crazy. You know the only reason they don't like you is because they think you never care about anybody. If they knew what you'd done, they'd all be your friends!"
"I don't need friends."
"Everybody needs friends, Severus," she shot back. "Even a cold fish like you."
Snape gave a humourless laugh. "Oh, wouldn't it be nice to be that childish and innocent? It's not about friends, Lily."
"Then what is it about?" she demanded.
"Enemies." He held her gaze, suddenly deadly serious. "There's something coming, Lily. The Ministry of Magic might not believe it, but Dumbledore knows it - and so do I. This is about more than just one potions teacher cracking up and hexing a student." He paused for a second. "The dark is coming, Lily. And if we don't have somebody right there where the dark is thickest watching for it, it's gonna be too late."
Lily's ire faded into something approaching resignation. "And you think that person's you?" she asked.
"I'm the only one it can be, Lily," he told her. "I'm the only one that knows what to watch for... and the only one that has a chance at getting on the inside. So right now, the worst thing I can have is friends. I need enemies, because all they understand is enemies. I need them to believe that I'm as bitter and twisted up and jealous as they are. So as of right now, I'm turning my back on friends." He hesitated for a fraction of an instant. "And that includes you."
He turned, and walked back up the steps and out of the dungeon without looking back.
That was the last time Sev spoke to Lily that year.