Severus Snape was on edge. It had been two months since the start of the school year, and his suspicions about Quirrell had only grown stronger. The man lingered near the third-floor corridor more often than any professor had an excuse to, and there were moments, brief glimpses, when his cowardly demeanor and stuttering seemed to drop, entirely. Severus didn't like it.
It was Halloween, the anniversary of Lily's death, and judging by Potter's behavior at breakfast, the boy had no idea. That seemed wrong, somehow, but on the other hand, Severus did not want to ruin one of the biggest feast days on the Hogwarts calendar by shoving the boy's parents' deaths in his face, either.
After the feast, perhaps, he would pull the child aside, and they could light a candle for Lily together.
He would be lighting one, either way. It would be petty to exclude the boy.
It was also the anniversary of the albeit temporary defeat of the Dark Lord, and Lucius Malfoy was insisting that Severus join him for some sort of late-night vigil.
There was no telling whether Lucius was intending to showcase his stalwart loyalty to their fallen leader, arrange a meeting amongst non-incarcerated Death Eaters for his own gratification, or trap Severus into a face-to-face encounter, to glean the maximum level of detail regarding Harry Potter's life.
Severus had been avoiding Lucius as often as he could. Rumors within Slytherin regarding Potter's magical acumen, social gravitas, and political beliefs ran wild. Or, perhaps more accurately, they slithered wild, beneath the notice of the other houses, but fast-spreading, and no-doubt exaggerated.
There was no telling what young Draco had relayed to his father, so Severus would likely be unable to hold any of the rumors back, unless he was able to maneuver Lucius into jumping to his own conclusions and leading Severus' report.
Thankfully, Severus had mostly Ravenclaw and Hufflepuff classes for the day, which led to considerably fewer headaches and explosions than the Gryffindor and Slytherin counterparts, although they were also less fun. Severus was distracted enough with the day's heavy meaning and obligations, that he was not in the mood to make Gryffindors' cry, or splutter with rage, today.
By the time the Halloween Feast was set to begin, Severus was morose and agitated. He snapped waspishly at the other professors, as they took their seats, but quickly took advantage of Quirrell's tardiness by seating himself between Minerva and Pomona before the turbaned man could force himself within Severus' direct vicinity, yet again.
It was odd, that Quirrell was absent. Worrying, perhaps.
Severus sipped his pumpkin juice and scanned the absurdly decorated hall. Potter was present. Good. If something happened, Severus did not want to be torn between tracking down Quirrell and keeping Harry safe.
Would Quirrell really do something as obvious as skip a feast in order to poke around the entrance to the philosopher stone's hiding place, unimpeded?
If there was a disturbance, everyone else in the castle would have an alibi, and he notably would not. It seemed a foolish move.
Where was the man?
The doors to the Great Hall opened with a bang, and Quirrell ran inside, shouting about a troll in the dungeons, before dropping into a faint.
Perfect.
Before he could move, or even open his mouth, Headmaster Dumbledore had ordered all the of the students to be evacuated to their dormitories.
Severus rolled his eyes. The Slytherin dorms were in the dungeons. The very same dungeons where a troll was purported to be on the loose.
"Higgs!" Severus called over the cacophony of scrambling students and shouted orders.
"Yes, Professor?" Higgs asked, running to Severus' side.
"Scout ahead as you go. If the troll is anywhere near the Slytherin dorms, turn around, and bring everyone back up here. Be smart, and be safe."
"Yes, Professor," Higgs said with a sharp nod, before turning to rally the Slytherin prefects.
Severus double checked that Potter was with the other first years, and then ran out of the hall, towards the dungeons.
He rounded a corner, placed a disillusionment spell on himself, and then circled back. He watched the limp form of Quirrell as the hall emptied and, sure enough, as soon as the coast was clear, the man stood, and hurried off in the direction of the third floor.
Severus followed, moving fast.
He knew of the damned Cerberus guarding that corridor. If Quirrell set the creature lose, it would make a mere troll look like pixie in comparison.
Rounding the final corner, Severus saw that the entrance to the corridor was already ajar. Cursing under his breath, he drew his wand and crept forward.
His senses were on high alert, focused entirely on the deep snuffling and growling coming from the next room.
Suddenly, he was falling forward. He'd been shoved from behind! He landed awkwardly on his knees, face to face with one of the beast's three heads, and heard the door slam shut behind him.
Severus shot a stinging hex at the dog's closest nose, and rolled to the side.
The Cerberus snapped at Severus, who mostly evaded the attack, but felt sharp teeth graze his calf.
He fired hex after hex at the creature, blinding it, stunning it, and confusing it, as he limped back towards the door.
Not even testing it first, Severus fired an unlocking spell at the door, yanked it open, and dove through, relocking it behind him.
He scanned the hallway warily, as he caught his breath. There was no one there. No one he could see.
His heart was pounding too loudly for him to make out any sounds of movement.
He did, however, hear the shrill, childish scream.
The troll.
He limped toward the noise, wand gripped tightly in his hand, Quirrell forgotten. There was a student in peril.
He met with Minerva, who had also heard the scream, and then Quirrell, conveniently, came up behind him.
Severus glared at the man, who could not quite hide his annoyance behind his mask of dramatic terror.
Together, the three of them closed in on the sounds of childish whimpers and breaking porcelain.
They found Granger, gripped in one of the mountain troll's vice-like hands, stabbing at the monster with her wand, as if it was a knife.
Minerva immediately threw spells to free the idiot girl, while Severus fired hexes at the troll's eyes, the least magically resistant points of attack.
The troll went down. Granger collapsed in a limp heap, alive, but badly injured. Quirrell sank down onto one of the toilets to catch his breath.
Severus fumed.
Quirrell had set this up. He had let the troll into a castle full of children, as a distraction so he could get his hands on a rock, and one of those children had nearly died.
"If you ever endanger the lives of one of these students again, I will kill you," Severus hissed at the man, who flinched back.
"I-I d-d-don't-t…"
"Save it. I can't prove it was you, but I know."
The man made a show of cringing back from him, but his nod seemed genuine.
He recognized that Severus was a threat.
Good.