"TROLL! IN THE DUNGEONS! TROOOOOOOLL IN THE DUNGEONS!" Quirrell screams, as he comes bursting in through the doors to the Great Hall, running all the way through the hall, until eventually he reaches the staff table, murmurs "thought you aught to know", before passing out.
Only a few seconds later, complete pandemonium erupts all throughout the Great Hall, as students begin to practically clamour over one another in some sort of effort to escape.
However, amidst all the chaos, Harry begins to push past all the fleeing students, taking advantage of the insanity of it all, he then quickly bends down towards the back of Quirrell's head, and throws away his turban, only to see another face staring back at him. "HOLY FUCK!" He screams, as the voice begins to speak, a wheezy, raspy sounding voice. "Harry Potter..." However, Harry is in no mood to deal with this. "FUCK THIS SHIT I'M OUT!" He calls over his shoulder, as he quickly begins retreating from the hall, along with the rest of his peers.
Screams of absolute terror can be heard echoing across all of Hogwarts, which can even be heard from Hogsmeade itself!
Finally, when the pair of them make it back to Gryffindor common room, Ron turns to Harry and asks him "What did you see back there, mate?"
Harry just collapses into the nearest armchair, appearing almost as if he had aged by a thousand years, before responding. "Don't even fucking ask." Harry mutters, as he suddenly finds himself wondering what beer tastes like.