The Great Hall went silent for a full second after Quirrell crashed through the doors.
Then it didn't.
Children screamed. Benches scraped back. The enchanted ceiling above them churned with sudden cloud, as if the castle itself had flinched. Quirrell lay face-down on the flagstones, one arm outstretched, and said nothing further.
"Silence."
Dumbledore's voice didn't rise. It didn't need to. It simply arrived, and the noise stopped.
He stood at the staff table with the particular composure of a man who had lived long enough that very little surprised him, and issued his instructions in a calm, carrying tone — prefects to lead their houses back to the common rooms, professors to follow him. The hall began to organise itself with the clumsy efficiency of several hundred frightened people trying to do as they were told.
In the press of Gryffindors moving toward the door, Harry caught Ron's arm. "Hermione and Kevin don't know. They're still downstairs."
Ron nodded. They peeled off from the group and ran.
Kevin heard it before he saw it.
The floor vibrated — a slow, rhythmic thud that climbed up through the stone and into his boots. He was standing in the corridor outside the girls' bathroom with his back against the wall and a book open in his lap, and he closed the book, stood up, and looked toward the far end of the hall.
The shadow came first. Then the club — longer than Kevin was tall, dragged along the floor and leaving a scored line in the stone. Then the troll itself, filling the corridor the way a boulder fills a doorway, its grey skin slick and its small eyes catching the torchlight.
Kevin pulled his wand.
They looked at each other for a moment — the troll blinking with the slow cognition of something that had never needed to think quickly, Kevin calculating with the fast cognition of someone who had read about trolls and was now revising several assumptions in real time.
Then they both moved.
"Sandstorm!"
Yellow sand erupted from his wand and spun into a whirling column that swallowed the corridor in a grinding, stinging cloud. The troll lurched sideways, club swinging at nothing, its small eyes clamped shut.
It wouldn't hurt the thing — mountain trolls had the magical resilience of a stone wall, and anything a first-year could throw at it would bounce off without registering. But the sand bought seconds, and seconds were what he needed.
The bathroom door cracked open behind him.
"Kevin? What's — " Hermione's head appeared in the gap, eyes wide, her earlier distress entirely replaced by something more immediate. She took in the yellow storm, the massive shape thrashing inside it, Kevin standing between her and it with his wand raised.
"Back inside," Kevin said, without turning around. His voice was steady. "Lock the door. Professors will be here soon."
"I'm not going to just —"
"Hermione." He glanced back, just for a second. "Please."
She looked at him. Then at the troll, which had stopped swinging its club and was now turning its head slowly, the sand thinning as the spell spent itself.
She went back inside. He heard the lock click.
The troll found him again through the dissipating cloud. Kevin tried a Tripping Jinx — the troll stumbled, caught itself on one enormous hand, and kept coming. He tried a Binding Hex. The troll walked through it.
Right, then. Spells weren't the answer here.
"Featherlight. High Speed. Bulwark."
The enhancement charms settled over him like a second skin. The weight left his limbs. The corridor seemed to slow slightly, the troll's lunge arriving in a frame he had time to read.
The club came down.
Kevin wasn't there. He'd moved left and forward simultaneously, using the downswing as a launch ramp, vaulting up off the shaft of the club as it hit the floor and landing on the troll's right shoulder. He had perhaps half a second before the thing registered the weight.
He used it.
His wand went into the troll's eye like a dagger — not a spell, just physics, the blunt end driven in hard. The troll's roar shook the walls. Its hand came up and wrenched the wand free and snapped it in one motion, and Kevin was already pushing off, landing in a controlled drop five metres back.
The troll spun. Green fluid ran down its face. It was furious and it was hurt and it still had two and a half functioning eyes and the full weight of four hundred kilograms of irate mountain troll.
Kevin looked at his empty hand where his wand had been.
Then: "Wingardium Leviosa!"
The troll's club jerked upward and floated away from its grip, drifting toward the ceiling. Harry and Ron came skidding around the corner at the far end of the hall, wands out, faces white.
"Run!" Harry shouted.
"Can't," Kevin called back. "Hermione's behind me. Draw it this way — I'll keep its attention."
He didn't need to work hard at it. The troll had forgotten about everyone else. It was looking at Kevin with the focused, total attention of something that has decided a particular problem needs to be resolved.
No club. It reached for him with both hands instead.
Kevin backed up, keeping just ahead of the grab, the enhancement charms keeping his footwork quick. Ron, from the far end of the corridor, had spotted the floating club. He raised his wand, aimed, and dropped the spell.
The club fell.
Onto the troll's head.
The troll sat down. Not gracefully. The floor cracked under the impact and it sat there making a sound that started as a roar and became something closer to a whimper, its remaining good eye glazed.
Kevin stood still. Watched it. Waited.
It listed sideways and didn't get up.
He let out a long breath and sat down on the floor.
The enhancement charms faded. The adrenaline did not. His hands were shaking slightly, which he found informative about the gap between managing a situation and being completely fine about it.
Snape arrived first — he came fast, reading the hall with a single sweeping look, and his wand was already up. Three precise cuts from twenty feet away and the troll's neck, arms, and legs opened in long, clean lines. It collapsed fully and went still.
McGonagall came through the door at a run. Quirrell arrived last, slightly out of breath, looking at the troll with an expression Kevin filed away without comment.
McGonagall swept the four students behind her with one arm and looked at the troll with the expression of someone who has many feelings about what they are seeing and is choosing to defer them.
"Is everyone —"
"Hermione's in the bathroom," Kevin said. "She's not hurt."
McGonagall went to the door and knocked twice. It opened immediately, as though Hermione had been standing directly behind it. She came out pale but composed, took one look at the troll, and pressed her hand over her mouth for a moment before lowering it.
"All right," Kevin said, from the floor. "Mostly."
Hermione looked at him properly then — sitting on the cold stone, no wand, hands shaking — and her expression shifted into something that had nothing to do with composure.
"Who do I speak to," McGonagall said, with the tone of a woman who has decided to be professionally furious rather than personally terrified, "about what in Merlin's name has happened here?"
Heads dropped. The students looked at Kevin, who was still on the floor and showed no sign of taking the lead.
Hermione straightened her shoulders. "It was my fault, Professor. I read about trolls and thought I could handle one on my own. It was stupid. If Kevin hadn't been here —" she paused, "— and Harry and Ron —"
"I see." McGonagall studied her star pupil for a long moment. "I am very disappointed, Miss Granger."
Hermione looked at the floor.
Harry glanced toward the staff. Snape had shifted his weight, and in the torchlight the dark fabric over his leg showed something wet and spreading. The moment Harry looked, Snape noticed and angled himself so the leg was in shadow.
"Five points from Gryffindor," McGonagall said. "For recklessness of the first order."
Kevin raised one hand from the floor. "Professor — "
"You," she said, turning on him, and her voice had an edge that Kevin had not heard before. Not anger. Something closer to the aftermath of genuine fear. "Five points each for the three of you who came to help. That is not a reward for running toward a mountain troll — it is an acknowledgement that you are still alive, which is more than you deserved."
"I was going to ask for ten," Kevin said.
"You do not get ten." She levitated him off the floor with a single, rather firm flick of her wand. "You get five and my profound relief that I am not writing to your headmaster tonight to report a casualty. Move."
She ushered them out. Behind them, Quirrell stayed to deal with the troll.
Snape left before anyone could ask about his leg.
The hospital wing again. Madam Pomfrey tutted over Kevin's wand hand and declared him physically uninjured but magically exhausted, which Kevin chose to interpret as a compliment.
Snape appeared briefly, set a potion on the bedside table and a replacement wand — blunt, slightly crooked, acquired from somewhere Kevin decided not to ask about — on the blanket beside it, and left without comment.
Harry, Ron, and Hermione crowded in the moment Madam Pomfrey's back was turned.
Hermione sat on the edge of his bed and took his hand.
She didn't say anything. Didn't need to. She'd heard the things he'd said in the corridor — back inside, lock the door, professors will be here soon — and she'd understood what they meant, and the understanding had been sitting in her chest since the lock clicked.
Kevin squeezed her hand once.
Ron, on the other side of the bed, was going through his own private reckoning with what had happened in the corridor. His ears were red. He opened his mouth, closed it, looked at Hermione, and said: "I'm sorry. About earlier. What I said was — I was being a prat."
Hermione looked at him.
"I was. I'm sorry."
"It's all right," she said, which wasn't quite forgiveness but was a beginning.
"No," Ron said, surprising himself slightly, "it really isn't. But I'll be better."
Harry, who had been watching all of this, chose the moment to defuse the weight of it: "Kevin, if you keep ending up in the hospital wing, Madam Pomfrey's going to name a bed after you."
"She already has," Kevin said. "She calls it the Problem Child cot. I've been informed."
They laughed. Hermione pressed her forehead against Kevin's shoulder, still holding his hand.
He looked at the ceiling. Thought about the Philosopher's Stone, still sitting somewhere under the castle, about Voldemort on whatever battlefield came next, about all the long years of plot between now and the end of it.
He was going to need a better wand.