[The chapter title is preserved, though the content has been integrated into the preceding chapter's climax above and the immediate aftermath is continued here.]
The moment he appeared on the train roof, Kevin had already understood the shape of the play.
Hundreds of Dementors dispatched to lock down the Hogwarts Express, arriving simultaneously with the attack on the Grangers. Voldemort had never intended for the Dementors to accomplish anything on their own — he'd expected them to freeze Kevin in place, buying time and resources for the actual operation. And if Kevin broke free and Apparated directly to the Muggle neighbourhood, the Death Eaters there could operate openly, knowing that any magic Kevin used would light up the Ministry's detectors. He'd be outnumbered, exposed, and legally compromised simultaneously.
It was, Kevin thought as he launched his Patronus and felt it hit the swarm with everything he'd packed into it, a reasonably good plan.
The goldfish blazed white across the carriage roofs. A massive ring of Patronus energy detonated outward, scattering Dementors in every direction — not a targeted strike but a pulse, carving breathing room. Kevin's voice went through the Amplification Charm in the same instant:
"Harry — protect everyone."
He Disapparated before the echo died.
Back on the train, the temporary respite lasted perhaps forty-five seconds before the Dementors began regrouping.
Harry's group — trained, experienced, purposeful — was already moving. The advanced class students who could cast Patronuses were outside or hanging from windows; the rest were running the evacuation. Even the Slytherins played along without being asked, corralling younger students toward the centre carriages with a brisk practicality that surprised everyone who noticed.
Sirius ran interference like a man who had been waiting years for an excuse to cut loose.
But the Patronus casters were burning through their reserves fast. Holding a Patronus against this many Dementors, for this long, took a toll — Kevin made it look effortless because Kevin was Kevin, but for a fifth-year doing it for the third time in an emergency, the magical drain was brutal. One by one they started dropping, each withdrawal opening a gap in the shield perimeter.
Harry closed the gaps as they appeared — a stag Patronus thundering across the train roof, scattering the closest clusters — but it was running him into the ground.
"Harry." Sirius caught him before his knees hit the floor. "No more. You've done enough."
"I'm fine."
"You have a nosebleed and you're shaking. You're not fine."
Harry didn't have a good answer for that. He allowed himself to be sat down, still watching the windows, still counting the shapes moving outside.
Hermione had one hand on her bracelet. Something was changing. She could feel it — the faint pull of it shifting, direction reversing, distance shrinking.
"He's coming back," she said quietly.
Then a sound like a thunderclap at close range rattled the windows, and something plummeted through the clouds.
A figure. Moving fast. And ahead of it, streaming outward, a blast of white Patronus energy so concentrated it looked almost solid — a goldfish-shaped light that hit the surrounding Dementor swarm like a cannon shot and threw them in every direction at once.
Kevin landed on the roof with the casualness of someone stepping off a low wall, cushioning charm doing the actual work.
"Well done, Harry," he called down through the carriage windows — loud enough to carry over the chaos, warm enough to actually mean it — and fired the second pulse of his Patronus into the retreating swarm before any of them could think about coming back.
They didn't.
Hermione crossed the gap between compartments at something just below a run and wrapped both arms around him before he'd fully processed that she was in motion. Her face was in his shoulder. She didn't say anything for a moment.
"They're all right," Kevin said, arm coming around her back. "Both of them. I promise."
She stayed there for another few seconds, and then she nodded once against his shoulder and straightened up.
The others hung back, giving them the space, reading the scene correctly.