The Order of the Phoenix spent that month preparing for battle. They knew that Voldemort would attack soon—Snape had been able to tell them that much. They had also guessed that the upcoming battle would involve the dementors, but they knew nothing of where or how Voldemort would strike. Harry often stayed up until morning with the other members of the Order, discussing strategies, or checking the castle wards with Albus or McGonagall. But though he sometimes caught sight of Snape at meetings or meals, he had not found another chance to approach the other wizard.

That Snape could not give them any concrete details of Voldemort's movements was a disturbing new development—even more so because it could be the first time any of them faced the dementors on a battlefield. For Albus had been right, of course. The dementors had joined Voldemort as soon as the war had started. What was the despair of a few dozen prisoners at Azkaban to the anguish of the battlefield? And so they became Voldemort's most terrifying followers: faceless, inhuman, immortal as war itself, unrestrained now by the Ministry's magic.

Voldemort was clever in staging the attack. There was little warning, for the Dark Lord had given even the most elite of his followers only the vaguest of details. Albus was unavoidably drawn away with an emergency at the Ministry as they struggled to deal with the aftermath of a full-scale attack by the Death Eaters at St. Mungo's hospital, leaving Hogwarts vulnerable.

The dementors attacked the castle from the Forbidden Forest. The wards gave only the barest warning before they were on school grounds, trying to force their way through Albus' shields.

Harry was on his way to assist with a seventh-year Defense Against the Dark Arts class when he heard the castle's warnings: a hollow throb like the beat of a great metal drum pulsing in time with the quickened rhythm of his heart. His mind raced at double speed through the day's schedule as he sprinted for the Great Hall: Gryffindor, Slytherin, Ravenclaw, Hufflepuff—Merlin, the First Years!

McGonagall and Snape were there before him. "Professor McGonagall, the dungeons!" he shouted above the clamor of bewildered, frightened students. Salazar Slytherin's wards would protect the students for a time even if the rest of the castle fell. She began leading students away with brisk efficiency, helped along by the rest of the teachers who had assembled there.

His eyes found Snape's through the chaos. The Potions master was at his side a second later, asking quietly, "What is it?"

"The First Year Hufflepuffs," he replied, taking a deep breath to slow his panicked heartbeat. "They're on the Quidditch field with Hooch."

Snape paled. "How long?"

Harry closed his eyes, reached. The shields were disintegrating faster than he would have thought possible. "A minute or two. They won't make it."

His Sunflare darted out into the Great Hall and slid to a smooth landing in front of him. He climbed on, and felt the broom dip behind him. "Don't argue, Potter," growled Snape's voice in his ear.

He wasted no more time. They zoomed upward and out of the open front doors, heading for the Quidditch Field at the limits of the Sunflare's speed.

He spared a moment of purely selfish gratitude for the heat and solid strength of the wizard at his back. The power, the unflinching calm. It helped to center his own magic, leaving his mind crystal-clear for the upcoming battle.

At the edge of the Dark Forest he could see a mass of black dots—five, ten, a dozen—two dozen dementors. Dementors, attacking the school in broad daylight—not like the last time, not with stealth and betrayal in the dead of night. Had Voldemort grown so sure of his power? Did he really think that the school could be overtaken like this?

He heard the slight intake of breath of the man behind him. But there was Madame Hooch's First Year class, flying towards them at a slow but steady speed in a tight mass, the best flyers in the class helping their peers on their desperate flight to safety. Not one of the children, not even the worst flyers, had been left behind.

As Harry watched, one boy's broom dipped alarmingly, as if it were about to take a nose-dive to the ground. He reached out instinctively with mind-magic, not knowing if he was strong enough to catch the boy if he fell, but to his relief the broom steadied itself almost immediately. And then he realized: Hooch was levitating those brooms to keep them afloat.

Snape at once drew his own wand to augment the Flying Instructor's spell. Harry felt the castle bugle another alarm as the shields buckled under the combined strength of the dementors. "Get them inside," he called to Snape, then flung his leg over the handle and dove off, leaving Snape in sole control of the broom.

He heard the man's quiet, succinct curse, but knew that the Potions master would require all of his concentration to maintain the Levitation spell.

Harry cast a cushioning charm on himself to soften the long fall. He hit the ground rolling and was up immediately, pointing his wand at the knot of dementors in the far distance. Albus was the only one who knew the complex spells that guarded the castle well enough to augment the shields, so he wove his own wards tightly against the castle's outermost protections, lending them a small amount of structure and support. While the shields held, the Hogwarts grounds would be safe from the dementors' poison; they would at least buy Hooch and Snape some extra time to get the children to safety.

The Hufflepuffs approached, almost skimming the ground, and to Harry's anxious gaze it almost seemed as if they were floating through an Impedimentia spell. He clenched his teeth as the castle shields buckled again and started to disintegrate like moth wings in dragon's blood, and shuddered at the first icy touch on his own wards. Hurry, he pleaded silently with the figures growing slowly but steadily closer in the distance, nails leaving bloody crescents in his arm. Please hurry.

He gasped as ice-cold talons burned into his shields. He sank to his knees, fighting to hold them against the inhuman strength of the dementors. Overhead, the first of the children flew past him. Just...a little longer.

Suddenly the castle's shields firmed, repelling the dementors back to the edge of the Forbidden Forest. "Albus?" Harry whispered. But the magic felt different; it was a steady, unwavering fire, not the deep flowing river of Albus' power. McGonagall! She's taken over some of the defenses!

He had a moment to be grateful for the respite before the dementors advanced again. Pressure built behind his shields with the cold, calculated fury of a bottled blizzard. He wove energy into them desperately. Please, just...

Behind him, the doors to the Great Hall slammed shut, and Harry smiled tightly. Then the blizzard hit.

[[center:***]]

Warmth at his back. Strong hands on his shoulders, supporting his weight. He blinked, shook his head slightly to clear it of the ringing left by the backlash of his shattered spells. In the distance, the dementors stepped onto the edge of the Quidditch Field and streamed towards them in a line of ominous black dots. He bit back a savage curse. Snape was supposed to be safely ensconced behind Hogwarts walls, not out here playing bait with him.

"Potter," Snape said, his voice strained with something that was not quite fear—something that was much bleaker—"cast your Patronus. I cannot."

Why? he wanted to ask, should have asked. But there was no time—no time in the single moment of permission to probe, to explore the voice that was as emotionless as if the black-cowled, faceless dementors bearing down on them had already sucked all memory of joy away. The air was chilling around them as Harry held out his wand and wove around himself a single happy moment as bright as the sun which he knew still shined overhead, though he could not feel its warmth.

"Expecto Patronum!"

The silver stag that was the memory of his father leapt from the tip of his wand, tossed its proud antlered head, and charged at the dementors. Harry heard a sharply intaken breath from the man beside him, but he dared not turn his head to see.

The dementors scattered and regrouped almost immediately. The stag charged again, keeping them at bay. Behind him he heard Snape chanting ward spells: layers upon layers upon layers. His Patronus reared, almost connecting with the nearest dementor before it glided away out of reach. There were so many of them...too many, and he was already drained. Albus. Albus, please. Surely he had felt the castle's alarm. Surely he would come in time. Surely...

But the dementors had grown too strong under Voldemort's rule. Even now Voldemort could barely command his army of faceless monsters, bloated with power on the terror of wizards and Muggles alike. They leeched magic away so swiftly that a single Patronus could stand against two or three dementors at best. Against two dozen dementors his Patronus had no chance.

He jerked on Snape's sleeve as his Patronus began to fade, attempting to give some warning. The stag lowered its antlers and rushed the advancing line of dementors once more. The dementors slowed, but did not stop. The Patronus was as faint as sun-touched mist now, but it reared defiantly, kicking out again and again at the black figures that were moving slowly to encircle it.

A hand grabbed Harry's collar and shook him briefly. His eyes focused with effort on Snape's face. "Run, damn you. Run!" the Potions master shouted.

But he was rooted to the spot, unable to turn his back on the silvery, faintly-glittering shape of his Patronus, still valiantly fighting while the dementors drew closer like a pack of slavering, ravenous hyenas. Snape gave him a shove that sent him tumbling to his knees and yanked him up again, jerking them both into an awkward, stumbling run towards the great oak doors of the castle.

Harry gave an incoherent cry as the Patronus flickered and faded away, but did not stop. A few moments later, it was he who had to support Snape with a hand at the elbow when the dementors breached the Potions master's wards. Snape shuddered hard and fell against Harry, his face bone-white with strain. The dementors approached with inhuman speed, sending despair before them like a miasma of poison. "We won't make it," Snape gasped. He raised his wand and cast a shower of sparks into the mass of black cloaks. That slowed them, but only for a moment.

Harry dragged Snape with him, fueled only by sheer stubbornness and determination, refusing to look back at the line of dementors gaining too quickly on their limping run. "We'll make it," he gritted out grimly with the little breath he could spare. But he knew that Snape was right. At the rate the dementors were approaching even his Sunflare would be hard-pressed to fly both of them to safety. And Snape was out here with him when he could have been safe behind the castle walls...

His broom swerved overhead and drew parallel with them. He shoved Snape onto it and bound him there with the strongest binding spell he could summon. "Go!" he screamed at the Sunflare, carefully not looking at Snape as he gave it a push that propelled it with the speed of a lightning bolt towards the castle.

His second attempt at a Patronus failed utterly; he had neither the energy nor the concentration left for the summoning. Instead, he began to throw torrents and torrents of sparks into the path of the dementors, hoping to slow down their advance, to get Snape to safety, to buy time for Albus to return. When he had not even energy left for that, he drew fading afternoon light from the sky, feeding it with the illusion of light in the mirror of his mind, and sent it flaring across the field in one last desperate attack. The shadowless figures seemed to flinch back a little at that, but try as he might he could not hold onto the spell, and as the light faded he fell back onto the ground gasping weakly, his eyes filled and blinded with the sky.

"Get up, you stupid boy," the too-familiar voice growled into his ear while hands tugged insistently at his arms.

"Merlin on a miserable stodgy mule!" he snarled weakly, trying and failing utterly to leverage himself off the ground. He'd failed, and they were dead—worse than dead.

"Look." There was an odd subdued note in the dark voice.

He was finally able to raise his head to see—

A wave—a torrent—a river of white, thundering towards them from the Forbidden Forest, towards the black figures that hesitated, wavered, and ultimately broke against the wall of shimmering whiteness. Unicorns, his dazed mind finally registered, more than he had ever dreamed of seeing, galloping—flying—across the field with mane and tail of snowsilk flowing behind with the swiftness of their passing. Unicorns—grace made flesh, long slender horns burnished gold in the afternoon sunlight, fierce beauty burning away the insidious, numbing cold of the dementors.

He gasped, realizing only now that he had forgotten how to breathe, that tears were sliding unnoticed down his cheeks, that the figure kneeling beside him had gone utterly, deathly still. A joyful note arched above him, and he tilted his head to see a streak of crimson overhead. Where it landed he could finally make out Albus Dumbledore, wand flaring with light, face a mask of terrifying anger. That approaching figure raised his wand, and the unicorns responded, imprisoning the dementors in a tight circle with deadly horns lowered.

"Begone!" Albus thundered in a voice that Harry was sure had carried to the students hidden in the dungeons of Hogwarts. When the wizard raised his wand once more, it blazed with a light much brighter than that of the last of the sun's rays. A great bird—a snowy phoenix made of pure silvery light—rose from the tip of that wand, circled once above their heads, and then dove toward the knot of dementors imprisoned by the unicorns. At its touch the dementors suddenly flickered in place and disappeared as if they were wisps of smoke blown away by a blast of wind.

Harry turned to Snape. "Professor..." he began, but stopped abruptly. The other man seemed to have turned to obsidian there beside him, the only incongruous spot of darkness left in a sea of white and green. In a face left without any color at all, the wide black eyes staring at the unicorns were an endless, churning abyss. Stunned, Harry raised a hand, and let it fall without touching the other man.

"Professor..." he said again, but this time so softly that he did not think the word could possibly have been heard. But the face turned toward him, eyes meeting—shattering—and he fell into darkness.