There it was, a solid fact, the place to start. Voldemort had stationed Alecto Carrow in the Ravenclaw common room, and there could be only one explanation; Voldemort feared that Harry already knew his Horcrux was connected to that House.
But the only object anyone seemed to associate with Ravenclaw was the lost diadem… and how could the Horcrux be the diadem? How was it possible that Voldemort, the Slytherin, had found the diadem that had eluded generations of Ravenclaws? Who could have told him where to look, when nobody had seen the diadem in living memory?
In living memory…
Beneath his fingers, Harry’s eyes flew open again. He leapt up from the plinth and tore back the way he had come, now in pursuit of his one last hope. The sound of hundreds of people marching toward the Room of Requirement grew louder and louder as he returned to the marble stairs. Prefects were shouting instructions, trying to keep track of the students in their own houses, there was much pushing and shouting; Harry saw Zacharias Smith bowling over first years to get to the front of the queue, here and there younger students were in tears, while older ones called desperately for friends or siblings.
Harry caught sight of a pearly white figure drifting across the entrance hall below and yelled as loudly as he could over the clamor.
“Nick! NICK! I need to talk to you!”
He forced his way back through the tide of students, finally reaching the bottom of the stairs, where Nearly Headless Nick, ghost of Gryffindor Tower, stood waiting for him.
“Harry! My dear boy!”
Nick made to grasp Harry’s hands with both of his own; Harry felt as though they had been thrust into icy water.
“Nick, you’ve got to help me. Who’s the ghost of Ravenclaw Tower?”
Nearly Headless Nick looked surprised and a little offended.
“The Gray Lady, of course; but if it is ghostly services you require—?”
“It’s got to be her—d’you know where she is?”
“Let’s see…”
Nick’s head wobbled a little on his ruff as he turned hither and thither, peering over the heads of the swarming students.
“That’s her over there, Harry, the young woman with the long hair.”
Harry looked in the direction of Nick’s transparent, pointing finger and saw a tall ghost who caught sight of Harry looking at her, raised her eyebrows, and drifted away through a solid wall.
Harry ran after her. Once through the door of the corridor into which she had disappeared, he saw her at the very end of the passage, still gliding smoothly away from him.
“Hey—wait—come back!”
She consented to pause, floating a few inches from the ground. Harry supposed that she was beautiful, with her waist-length hair and floor-length cloak, but she also looked haughty and proud. Close in, he recognized her as a ghost he had passed several times in the corridor, but to whom he had never spoken.