“Professor,” Harry started, “the diadem of Ravenclaw. I need to find it. It’s a Horcrux.”
“Then we go through the walls,” Ron muttered. “Literally. We know the secret passages behind the tapestry of Barnabas the Barmy. We can get to the seventh-floor corridor from the fourth-floor balcony if we use the old servants' stairs.” Harry Potter And The Deathly Hallows Part 2 -20...
“It’s the only way to end it,” Harry said. “Professor,” Harry started, “the diadem of Ravenclaw
Hermione’s hand found his arm in the darkness. “Harry, the Room of Requirement is a trap. Draco Malfoy already tried to bring Greyback in through there. It might be swarming with Snatchers.” “Literally
Before Harry could agree, a different sound cut through the din. Not a curse, not a scream. A footstep. Deliberate. Slow. And then another.
Harry hesitated, then pulled the Cloak from his head. Ron and Hermione did the same. McGonagall’s eyes widened for a fraction of a second at the second Cloak, but she didn't comment. She strode forward, her tartan dressing gown (she had been roused from her chambers) billowing behind her like a battle flag.
“The diadem,” Harry whispered, his voice barely a thread. “Rowena Ravenclaw’s. It has to be here, in the Room of Hidden Things.”