Several turns later, James was about to give up. He wasn't even sure he'd know his way back to the Gryffindor common room. The corridor here was high and narrow, with no windows and only one torch guttering redly near the archway he'd entered by. Closed doors lined the corridor on both sides, each one made of thick wood and braced with iron bars. Behind one of them, a gust of night wind made something creak, low and long, like the moan of a sleeping giant. The overall effect was rather frightening, but James couldn't quite bring himself to turn back just yet. He walked slowly down the corridor, the torch making his shadow stretch before him, flickering into blackness.

        "Hello?" he said quietly, his voice hoarse, just above a whisper. "Are you still there? I can't see you."

        There was no response. The corridor was growing colder. James stopped, squinting hopelessly into the shadows, and then turned around. Something flickered across the corridor inches from his face and he jumped. The white shape streamed through one of the doors, and James saw that that door wasn't entirely closed. Blue moonlight filled the space he could see through the crack. Trembling, James pushed the door and it creaked open. Almost immediately, the door caught on something, making a grating scrape. There were broken chunks of iron on the floor next to something long and black with a hook on the end. It was a crowbar. James kicked these aside and pushed the door further open, stepping in.

The room was long and dusty, cluttered with broken desks and chairs, apparently once sent here for repair, but long forgotten. The ceiling sloped down toward the back wall, where four windows glowed with moonlight. The window on the far right was broken. Glass glittered on the floor and one of the swinging panes hung crookedly like a broken bat wing. The ghostly figure stood there, looking down at the broken glass, and then turned to look at James over its shoulder. It had resumed its human shape, and James gasped as he saw the young man's face. Then two things happened simultaneously. The ghostly shape evaporated in a wisp of silvery smoke, and there was a crash and clatter from the corridor outside.

        James jumped and spun on the spot, peering out the door. He didn't see anything, but he could still hear an echoing clatter from the darkness. James leaned against the inside of the door, his heart thudding so hard that he could see dull green flashes in his peripheral vision. He glanced around the room, but it was completely dark and empty except for the cobwebby furniture and broken window. The ghostly man was gone. James took a deep breath, then turned and crept out into the corridor again.

        There was another, smaller clatter. James could tell by the sound of it that it was further down the corridor, in the darkness. It echoed as if it were coming from another side room. Again, James berated himself for having forgotten his wand. He tiptoed into the darkness. After what felt like an age, there was another open door. He held onto the stonework of the doorframe and peered in.

        James vaguely recognized the Potions storage room. There was a man in it. He was dressed in black jeans and a black shirt. James recognized him as the very same man he had seen the morning before at the edge of the Forbidden Forest, sneaking photographs. He stood on a stool, examining the shelves with a small penlight. On the floor by the stool were the shattered remains of a couple of small vials. As James watched, the man stuck the penlight in his teeth and groped for another jar on the top shelf, keeping a precarious hold on the opposite shelf with his free hand.

        " Heritah Herung,"he read to himself around the penlight, craning his neck to direct the light onto the jar. "What the heck ith thith thtufh?" His voice was a low, awed mutter. Suddenly, the man looked toward the door. His eyes made contact with James, and for a long moment, neither moved. James was sure the man would attack him. He was obviously an intruder, and James had seen him. He tried to will his feet to turn and run, but there seemed to be some disconnect between his brain and his lower extremities. He stood and stared, gripping the stonework of the doorway as if he meant to climb it. Then the man did the last thing James expected. He turned and ran.

        He was gone almost before James realized it. The curtain at the back of the storage room still swayed where the man had blown through it. To James' great surprise, he darted to follow the man.

        The Potions storage room led into the Potions classroom itself. Long, high tables stood in the darkness, their stools tucked neatly beneath them. James stopped and cocked his head. Footsteps echoed from the corridor beyond. His own feet smacked the stone floor as James dodged around the tables and out into the corridor, following the man.

The man was hesitating at a point where two corridors crossed. He looked desperately back and forth, then glanced up and saw James coming. The man let out the same high, little shriek James had heard him make when he'd been chased by the ghost. He slipped on the stones, his feet seeming to run in three directions at once, then he mastered them and ran clumsily down the broader corridor. James knew where he was now. The man would come out onto the hall of the moving staircases. Even as James was thinking it, he heard another little shriek of surprise echoing back to him. He grinned as he ran.

        James stuttered to a stop at a railing and leaned over, peering intently into the darkness of the floors below. At first, the subtle grinding of the stairs was the only noise, and then he heard the clatter of the man's shoes. There he was, holding onto a railing for dear life and stumbling down a staircase as it swiveled ponderously. James hesitated for a moment, then did something that he'd always wanted to do but never quite had the temerity to try: he clambered up on the railing of the nearest staircase, straddled it, and then let go.

        The thick wooden railings, polished by generations of house-elves to a rocklike, glassy shine, were like beams of ice beneath James. He shot down the railing, craning his head over his shoulder to see where he was going. His hair, which had gotten lank with sweat in the minutes before, ruffled as air whipped past. When he neared the bottom, he gripped the railing again with both his arms and his legs, slowing, and then hopping lightly off the bottom. He cast around, looking for the man, and saw him clambering toward another landing, one floor below.

        James' dad had told him about the moving staircases, had explained the secret of navigating them. James gauged the moving labyrinth, and then chose another staircase just as it began to swivel. He swung himself over the railing and let go, streaking down it as if it were greased. On one side was the swaying chasm of landings, staircases, and halls; on the other, the speed of the blurring stairs. James gritted his teeth and craned to look behind him again. The man was just reaching the landing below. He stumbled, disoriented, as he backed off the staircase, and then looked up just as James rocketed into him.

        James hit the man at full speed, rebounded off him, and sprawled onto the flagstones of the landing. The man shrieked a third time, this time in frustration and surprise, as the force of the collision knocked him entirely off his feet. There was a piercingly loud crash, followed by a shower of tinkling glass. James rolled and covered his face instinctively. When silence descended again, James peeked through his fingers. There was a very large, roughly man-shaped hole in the stained-glass window at the foot of the landing. Through it, the spindly black fingers of trees swayed in a night breeze, scratching amiably at the star-strewn sky.