Harry Potter And The Deathly Hallows Part 2 -20... -

She looked at Harry one last time. Her eyes were wet, but her jaw was set like flint. “Mr. Potter. It has been an honor to be your teacher. Now go. And for Merlin’s sake, win.”

“That will take you directly to the seventh-floor corridor,” she said. “It bypasses the Grand Hall and the west wing, where the worst fighting is. Once you’re there, you’re on your own. I have a school to defend.” Harry Potter And The Deathly Hallows Part 2 -20...

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. She looked at Harry one last time

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.” Potter

“The diadem,” Harry whispered, his voice barely a thread. “Rowena Ravenclaw’s. It has to be here, in the Room of Hidden Things.”

“Professor,” Harry started, “the diadem of Ravenclaw. I need to find it. It’s a Horcrux.”

“Potter,” she said, not loudly, but with a clarity that cut through the chaos. “I know you’re here. I saw your Patronus—a stag—leading the house-elves to the kitchens ten minutes ago. Don’t insult my intelligence by denying it.”