Sev was roused before down by the sound of Malfoy rolling out of bed. "Ha! I woke you!" the blond-haired boy proclaimed delightedly. "So you do sleep."

"Occasionally," Sev allowed. "Don't tell the others. They might start thinking I'm a human being."

"Small chance of that," he smirked in reply.

Malfoy might be bright and bouncy with the prospect of the day ahead, but the rest of their dorm were less than thrilled to be woken so early.

"Why do we have to get up now?" grumbled Avery. "We're not even doing anything 'til noon."

"D'you want to be caught sneaking out?" demanded Malfoy fiercely. "You can sleep in the tunnels for all I care, but we have to be out of here before anyone else is awake to see us. We are not getting caught over this." This was Malfoy's big chance, his first real command situation. Sev didn't think it was purely logic that had compelled him to leave his biggest rival in the rear-guard position. Malfoy didn't want him to be anywhere that he could grab a slice of the credit for this operation.

The other boys departed, still bickering nervously amongst themselves, and Sev settled down with a book to await their usual breakfast time.

Sev seldom ate breakfast, but this morning he went down to see the house-elves and got several rounds of toast. He also picked up the kind of full English breakfast Colin always ate, and Malfoy's favourite cereal. It took a hover charm to get it all to follow him through the corridors.

Professor Ephemeria, striding through the corridors with a harried expression, stopped him with a frown. "Where are you going with that little lot, Severus? You know you're not supposed to eat in the dorms."

"It's a revision session, Professor," he lied automatically.

The Potions professor looked stern. "Leaving it a little late, aren't you?" The fourth year exams had already started; they had only a few days to go before they were finished. Fortunately for Malfoy's little plan, it was Divination today, a class that none of the five of them took.

"It's not me who has to revise," Sev pointed out with a shrug. Professor Ephemeria looked sceptical. Teachers didn't like to admit that there were students who could get their good grades without studying; it rather poked holes in their 'if you don't work, you'll never get anywhere' spiel.

Sev didn't mind getting caught; in fact, he'd rather counted on it when he'd set the food to hovering. Although Professor Ephemeria hadn't so much as glimpsed Malfoy or the others, if anybody asked her she would now remember that they'd been huddled in their dorm, revising over breakfast.

This pretence set up, he headed for his usual early-morning haunt; the library. There was almost no one there in the summer months, at least not when it was too late to cram for exams, and it was an unmissable chance to browse the shelves in private. Nothing would be happening for several hours, and the most he was likely to do by hanging about was call attention to himself.

However, about half an hour before the tests were due to start, just as he was contemplating getting into some better position to observe, there was a complication.


She casually breezed into the empty library and sat down across from him; exactly as if they were back in the First Year and he was still tutoring her for Potions on the quiet. Then it hadn't mattered so much if anyone might come upon her chattering away to Snape; she was new, she wasn't wizardborn, the whole Gryffindor vs. Slytherin thing might not have sunk in for her yet. Certainly it would take more than a cursory glance to get the impression Snape was even paying attention to her.

Now, though, things were different. Battle lines had long since been drawn, and Lily and Sev were not just on opposite sides but right in the thick of them.

James Potter - who, despite countless denials on both sides was very definitely something approaching a boyfriend - would have a hard time wrapping his head round the idea of Lily making friends with a Slytherin. His head would probably explode if someone added the name 'Snape'; thanks to his own anti-publicity campaign, Sev was regarded as every bit as maliciously dangerous as Malfoy - and smarter.

For Sev, the consequences of fraternising with the enemy were a little bit more severe than a little domestic strife. If talking to a Gryffindor was a hanging offence, being seen in company of a 'mudblood' was a thousand times worse. Being seen with Lily could destroy everything he'd built with the Death Eaters.

Of course, Lily wasn't stupid enough to not know that. "What do you want?" he asked without preamble.


"Don't we all?"

"I thought you had all of them?"

"Yes, but my parents never taught me to share." It was strange how easily they clicked into the old patterns of conversation. He and Lily just seemed to have the exact same vein of quick, dry wit, sparking off each other without thinking about it. Malfoy and Nick Avery were both far from mentally slow, but the suspicious atmosphere of their house somehow precluded quickfire banter; amongst Slytherins, words were carefully considered and weighed for the best effect. Witty banter was about give and take, but house Slytherin was about coming out on top.

"What's happening?" she demanded.

"Many, many things," he said, shovelling his books into his bag. "Anything in particular you had in mind?"

"You weren't at breakfast," she observed. "None of you."

He quirked an eyebrow. "You're watching Slytherin eating habits?"

"I'm watching Slytherins," she corrected. "Looking for patterns, and things that don't fit them; I learned that from you."

"If you'd looked a little closer, you'd have seen me going down to the kitchens to get breakfast for the five of us. What does that tell you?"

"That you went down to the kitchens, and the other four haven't been seen yet."

He couldn't help nodding in acknowledgement. "Exactly. Now, if the Hogwarts staff weren't so easily fooled, we'd have less of a problem."

"So there is something going on!" she announced triumphantly. He gave her a wry look.

"Lesson two in being like me: squealing like that is not a good way to preserve your aura of knowing everything. Do you have your cloak?" She nodded and pulled it out of the bag. "Put it on. We're walking."

"Won't people notice you talking to yourself?" came Lily's muffled voice from the empty air beside him.

"They generally try to avoid getting that close," he said dryly.

"This is about those tests that are on today, isn't it?" Lily realised. She spoke quietly, but even so it was as well the corridors were quiet. Snape headed towards the outside of the building, where he knew the 'Aurors' would soon be making their arrival. "Is something going to go wrong with them?"

"No, in fact they're going to go very well. The inspectors are going to make such a good job of probing the defences they'll be inside before you know what's happening."

"Before they realise that they're actually Death Eaters," Lily breathed. He didn't need to nod to confirm it. Abruptly, he was pulled backwards as an invisible arm yanked him back into an alcove. A moment later, Lily reappeared, tugging off the cloak to stare at him. "They're going to bust into the school? They're going to break in and you know about it?"

He nodded briefly. "I'm their rear-guard." Sev smiled ironically. "I'm to see if anything's going wrong."

"You can call it off?" she asked, frowning.

"Not without a good excuse. A true excuse. We're all Slytherins," he reminded her. "None of us trust each other."

"So, what? You're just going to let them attack?" Her voice was rising in disbelief, so it was just as well the corridors were empty. Lessons were cancelled for exams, and those students who didn't have Divination today were either outside soaking in the sun or back in their dorms.

"The teachers will be defending, as soon as they realise what's happening," he pointed out calmly. "This is about fear, not tactics; there'll only be two of them, so they can't hope to do too much damage. Mostly they'll be causing chaos, but they're likely to have been told to gun for any Muggle-borns. You should stay out of sight," he added as an afterthought. "Keep your cloak on."

"And do what? Twiddle my thumbs?" Lily was furious. "What about the other kids from Muggle families? They didn't happen to stop you in the corridor, so they don't get an advance warning? Sev, they could get killed!" Actually, it was more James Potter than the mudbloods who needed to watch out, but getting into that was not really the way to calm Lily down.

"Don't you remember Audley Fletcher?" he reminded her. "I'll be on hand; both sides against the middle. It's what I do."

"You mean you'll save people's lives if it doesn't look like causing trouble?" She suddenly threw the bundled up cloak at him. "I've got a better idea. You wear this. I'm not hiding; I'm gonna be out there waiting for them, and if they start blasting, well, I'll blast right back."

She was spoiling for an argument, but if she thought Snape was going to be like James and get stupidly overprotective, she was wrong. He simply nodded, and took the cloak. "Good idea," he agreed mildly. "This'll make things simpler."

Lily stared at him for half a second, and then snorted laughter. "God, what the hell are you? I don't know if you're a snake or a robot, but you're sure as hell cold-blooded." She shook her head. "And I like you, God help me. I don't know if that makes me even more disturbed than you are."

"Anything's possible." He pulled the cloak on as they started walking again. They reached the outside doors, and he spotted James and his friends across the grass. "Look, there are your little Gryffindor friends. I'm sure they'll be happy to join the fight with you." That killed two birds with one stone; the Gryffindors would provide unquestioning backup to Lily, and Lily would give James some warning that an attack was coming.

"And you?" she asked out of the corner of her mouth.

"I'll be on patrol." He turned away, probably leaving her wondering whether he was still walking with her or not.

The invisibility cloak certainly did make things easier. They might watch him as Severus Snape, but as an invisible presence he could easily go undetected in the chaos that would ensue. And it would be chaos - half of the school were out here sitting on the grass.

The Aurors had agreed beforehand where they would be starting, to make sure the staff didn't miss anything. The Death Eaters wouldn't dare to deviate from that; they couldn't afford to reveal themselves until they were inside the defences.

Some tactical eavesdropping and knowledge of the first two tests had told Sev what to expect from the staff. There would be three teachers waiting to watch firsthand; he could see them from where he stood, Malachite, Parilia and Vitae. They were a long distance away from the actual point where the 'Aurors' would be busting in, however, watching through Omnioculars so as not to disturb anything.

Those of the staff who weren't involved with the exams would be watching on Spellographs. It was likely they wouldn't even realise when things began to go wrong; not until they started puzzling over the curses the Aurors were throwing about.

Dumbledore himself wasn't even at Hogwarts; as always in the summer, he was tied up in paperwork with the other wizarding academies. It was a grand old tradition for wizarding schools to stab each other in the back and accuse each other of making things easy on their pupils, and standards had to be agreed across the board. Given Durmstrang's involvement with Voldemort, it was likely their headmaster knew what was going on and had deliberately scheduled this meeting to keep Dumbledore out of the way.

He kept an eye on the three observing teachers, and saw when Professor Vitae made an abrupt hand gesture. Following her gaze, he spotted the two cloaked figures making their way towards the school.

Vitae must have used the Sonorus spell, because suddenly her voice echoed across the field. "Students, the defence inspection is beginning! You can watch, but please keep well away from the Aurors and make no attempt to interfere with their enchantments. Thank you." Sev knew this was one of Dumbledore's ideas; some of the teachers had objected to the students being present for this test, but the headmaster believed they should have the opportunity to see how well protected their school really was.

Of course, that was rather the Death Eaters' intention too...

He watched calmly as the two Aurors cautiously approached, scanning for wards. All eyes were on them, at least until their painstaking work become too boring to follow. He glanced over at Lily to make sure she wasn't about to explode into action, and was glad to see she was under control. The Death Eaters wouldn't make their move until the defences were breached, and attacking before they revealed would be a deadly mistake.

He cast his memory back and pulled the original shape of the defences into mind. There were two rings of outer defences that had to be defused before the Death Eaters could get in; they would be able to do so, but it was picky work and take a long time. The point of the first ring was to stun or otherwise immobilise the unwary - the nastiness of the effects depending on which professor had been responsible for the particular ward you stepped on. The second was a kind of anti-curse shield, through which most spells couldn't be thrown.

Beyond those two rings, he knew, it was all magical alarms - and he doubted very much whether the Death Eaters would mind setting them off. They wanted panic when they opened fire. It was the Immobilisers they had to get rid of, not the noisemakers.

The crowd soon lost interest in watching two cloaked figures carefully scanning every inch of the ground, detecting wards and then probing their nature very cautiously. Sev was intrigued by how practised they seemed at the work; clearly, somebody somewhere in the Death Eaters had Auror training.

He drifted over towards the group of Gryffindors. They were fairly close to the demonstration, and once Lily raised the alarm he could rely on the cover of their blazing spells to work his own.

"God, this is boring," groaned Sirius, lying flat out on his back and looking at the sky. "Can we go, yet Lil?"

"I want to watch this," she insisted, not looking at him.

"It's interesting," agreed Remus mildly. "In fact, I wonder if I can get a little closer. I'm sure that's a variation of those probe charms Malachite told us about."

"Come on," agreed Lily, dragging him forward eagerly. James followed, as did the invisible Snape, but Sirius held Peter back.

"Leave 'em to it, mate," he advised, bored. "Got your Exploding Snap cards? This is like watching paint dry."

Sev saw the tension suddenly grow in the shoulders of the nearest Death Eater. Was the curse-shield down yet? The second it was, they would probably start firing.

He had to stop walking abruptly to avoid slamming into the back of Remus, who had suddenly frozen. "What is it?" demanded Lily.

Lupin was staring fixedly at the nearer of the two 'Aurors'. "There's something... His robes, I smell... I smell blood!" Sev could smell nothing - but he knew there was a very good reason Remus Lupin's nose was considerably more sensitive than his.

It all seemed to happen at once. Perhaps the Death Eater was panicked by Lupin's words - perhaps he had simply finished what he was doing breaking through the wards. Either way, he reached quickly for his wand, his companion a beat behind him.

Right then, Lily did something nobody would have expected of her.

She screamed. Loudly. Piercingly. A scream to wake the dead, not to mention cut through the air and alert just about every student or teacher within four miles.

Go, Lily, thought Sev quietly to himself. The echo of the scream seemed to hang in the air long after the sound had ceased. The momentary stillness seemed to stretch on to infinity, and then...

"Death Eaters!" yelled James, levelling his own wand. Lupin made a sound suspiciously like a growl in his throat, and let fly with an Expelliarmus charm. The spell wasn't strong enough to deprive the Death Eater of his wand, but he fumbled to keep hold of it and lost whatever spell he was planning to launch.

Battle was joined. The two Death Eaters were trying valiantly to get their curses off, but they were facing attacks from all sides. Ironically, the explosively out-of-control duelling club had done far more to prepare the Gryffindors for combat than any properly handled lessons. These were student wizards who fought pitched magical battles two or three times a week.

Sev, in his invisibility cloak, stood calmly by, occasionally sending in a quick spell to nudge a wand off course when the Hogwarts defenders looked too slow.

The massed students had barely reacted, still too surprised, but he saw the three observing teachers hop down from their vantage point and come running. Ephemeria and Fractalis were coming too, charging towards them from the direction of the Forbidden Forest.

The Death Eaters' element of surprise had been well and truly busted. They had probably counted on being able to saunter in, pick their targets, and be blasting away before anybody had time to react.

Instead, there were hexes and curses flying so thickly no one had time to aim at anything. Pete Pettigrew was one of the first to go down, zapped with something which turned his legs to jelly. He and Sirius had come running, the dark haired boy startling the Death Eaters by leaping in and actually physically fighting them.

He saw James Potter grab Lily and shield her from a curse, crying out in pain as he went down under the force of Cruciatus. However, before the Death Eater had time to press home his advantage, Snape stepped in and zapped the wand out of his hand. The man groped for it quickly, looking around wildly to try and guess who'd shot the spell at him.

Suddenly Professors Vitae and Malachite were there, having left the short-legged Parilia behind in the dust. Vitae was trying to pull out her wand, but she seemed to have got it caught on something in the inside of her robes. "Do something, Carnus!" she snapped.

Professor Malachite had his wand in his hand and at the ready - and yet he seemed frozen, unable or unwilling to use it. "Attack!" Vitae urged him, but he just stood there helplessly.

Suddenly another voice rang out, loud enough to cut through all the chaos like a knife. It took a moment to place it, it sounded so different from Professor Fractalis's usual nervous stutter.

The long sequence of spell-words he used was completely unfamiliar to Snape; so much so that he was sure it had to be an original enchantment. Suddenly all around them, symbols appeared on the ground in blazing blue-white light. It was so powerful, everybody had to shield their eyes against it.

Apparently, Professor Fractalis's amazing geometric designs were a bit more powerful than he had let on.

Even Snape's unblinking stare wasn't enough to fight that blazing light, and he had to shut his eyes against it. When he could look again, the cloaked shapes of the Death Eaters were fleeing up the path. James and Sirius looked as if they were ready to go haring after them, but Professor Vitae held them back.

"Let them go, boys. You did a brave thing here, but you don't have the power to face them on their own ground." She scowled at Professor Malachite, who was looking decidedly embarrassed at the way he'd frozen up. Fractalis had gone bright red for a different reason, as Professor Ephemeria hugged him enthusiastically.

"Trigo, that was amazing!" she cried, and he went even redder.

It was all over bar the treatment of injuries and the alternate praising and scolding of the Gryffindors. Satisfied that the Death Eaters had been repulsed for the moment, Snape slipped silently away.

Lily caught up with him in a corridor on his way back to the quiet of the dorms. He turned to face her with a shrug, handing her the cloak before she asked for it. "Nobody died," he pointed out.

"Somebody will, one day," she said heavily. "This is a knife-edge, Severus, not even you can walk along it forever. Some day, sooner or later, people are gonna killed for this little scheme you're running. And then what?"

He looked at her for a long, unblinking moment, and then he said softly "Some must be sacrificed, if all are to be saved."

And after that, there was nothing more to say.