A\N: Hello again! Thank you for reading. I remind you that English is not my first language, so let me know if you find mistakes. Reviews are welcolmed.

Disclaimer: I don't own anything in the Harry Potter Universe, it all belongs to J.K. Rowling.

From the previous chapter:

In the meantime the girl had seen his shining Slytherin Prefect badge and had gotten up, looking in great discomfort. Apparently she didn't like to break rules, then.

"Oh. I – look," she said, glancing quickly at her clock. "I didn't realize it was so late. I'm sorry. I will get back to the Tower at once."

"Not so fast," he retorted. The girl looked resigned, maybe expecting him to deduct a million points from her House or something. He wasn't about to do that.

Gingerly, he aimed his wand against her face.

"Stupefy."

The girl woke up shouting. She sat on her bed kicking away the blankets and took her head between her hands, shaking. She touched her hair, resisting the urge to tear it away: the headache was so strong that even the presence of her hair was driving her crazy.

After a few seconds, she heard someone pull aside the curtains of her four-poster bed.

"Katerina?!"

Abigail, one of her roommates, was watching her wide-eyed.

"What's wrong with you?", she continued, as the other hadn't answered.

Katerina tried to show an apologetic smile. Her heart was beating fast.

"It's nothing. Sorry I woke you up," she whispered, moving to place her feet down on the soft blue carpet. For a moment, the world seemed to spin.

"You were yelling," said Abigail, looking a little annoyed. "I thought someone was murdering you… hey, are you ok?" she added, now with a slightly concerned tone.

"I'm fine, it's just a headache. And I think I had a nightmare."

For a moment, her head was again full of red flashes and blood. She couldn't remember what her dream was about, but she had to close her eyes in order to fight off the lingering dread that it still caused.

When she felt ready, she got up, reassured her other two roommates and stepped inside the bathroom. While the light magically readjusted itself according to her needs – not too bright – she looked at her reflection in the mirror. She was very pale, her long brown hair was disheveled and she had dark shadows under her eyes. Her hands were still shaking.

Her dark eyes in the mirror were staring back at herself. Then, slowly, her reflection shook its head.
"You look terrible," it said. "Go back to sleep."
Katerina let out a sigh and did as she was told.

Next morning, the Great Hall was unusually quiet.
The table of the Professors was completely empty; the students were whispering, while a small group of people was around a crying fourth-year Gryffindor girl.

"What happened to Barbara Hammond?" asked Katerina to Abigail while they were sitting at the Ravenclaw table.

Hayley Watson, the earliest-riser of their roommates, whispered:

"It's her sister. Yesterday night she was found near the entrance of the Hufflepuff Common Room." Hayley hesitated. "She was petrified."

Appalled, Abigail placed her pumpkin juice on the table.

"What, the Syndrome again?"

"Yes."

Katerina didn't speak. She didn't knew the Hammonds very well, but she knew that the youngest was just a second-year. She probably couldn't stand a chance against whatever had hit her.

Hogwarts School of Witchcraft and Wizardry wasn't the most ancient wizarding school in the world, nor the richest or the most appreciated; but its history over nine centuries long was the pride of the English magical tradition. Every non-Muggle British citizen was proud to send their children to the very school where the leading figures of the wizarding world gathered to teach, educate and protect young witches and wizards.

Those who were not blinded by pride, however, knew very well that Hogwarts was certainly not heaven. Only a decade before the school had been hit by a terrible scandal: the Defense Against the Dark Arts teacher was found guilty of using his students as test subjects for his experiments regarding Dark Spells. The professor was immediately fired and shut inside St. Mungo, the key of his cell was metaphorically thrown away and the whole story was partially hushed up.

And now, Katerina thought, the Headmaster of Hogwarts was dealing again with a problem that was potentially catastrophic for the public image of the school.

The first student found petrified had been a fifth-year Gryffindor, one of her classmates. For three weeks his body had been stuck, motionless, in the Infirmary; nobody seemed able to figure out a solution to wake him up from his magical coma. The school staff had tried to keep the news from spreading around, but someone had apparently told someone else that the boy had been hit by a mysterious magical sickness, and after a few days everyone was aware of it.

When the second victim, a third-year Hufflepuff, had been found in a bathroom on the second floor, the situation got out of hand. It was mid-afternoon, and half of the student body was there to watch the poor girl being slowly carried to the Infirmary.

Inside the castle everyone had their personal theory regarding what had happened, but the generally most accepted explanation remained the mysterious sickness. The students started to call it "the Syndrome"; and the victims of the Syndrome were now three.

"Do you think that now some students will decide to go home?", quietly asked Katerina to her Housemates.

"I heard that the Malfoy twins will soon go back to their French mansion," said Barnabas Carter.

"It won't be soon enough," Hayley complained. "Anyway, I surely don't want to go. I am certain that Headmaster Dippet will find a solution. And this year we have our O.W.L.s, we can't go home just like that."

"I really can't wait to see how you will study for your exams when you will be petrified too," said Barnabas sarcastically. Hayley shot him a nasty look.

"According to what his apprentice says, the Erbology Professor might have found a solution. He's trying to use the magical characteristics of the Mandrakes to create a potion that will wake the petrified students," declared Matilda Marchbanks. The topic of the conversation stayed on the characteristics of the Mandrakes until the end of the breakfast. No one of the Professors showed in the Great Hall.

After breakfast, while she was heading to Aritmancy, Katerina made her best to ignore the strange feeling that had tormented her since her awakening from the nightmare. She felt a fastidious prickling on the back of her neck, as if someone was intensely watching her. She turned her head a few times, looking for something that could explain that feeling, but didn't see anything out of the ordinary. When Abigail asked her if she was looking for someone, she just shrugged her shoulders and answered negatively. The other girl didn't ask further.

When the lesson finished, however, she felt that Aritmancy had done nothing to decrease her headache.

"You still have a migraine?", asked Matilda in a sympathetic tone. Katerina, hands covering her forehead and almost laying with her body on the desk, nodded unhappily.

"I do. I think I'll go to the Infirmary to get a painkilling potion. If I am late, will you apologize to Slughorn in my behalf?"

While the girls were nodding, Abigail piped, "I'll go with you. You are as white as a sheet and your eyes are blood-shot: you are frankly scarier than the Bloody Baron, and we don't want to frighten the little kids, do we?"

Katerina stared at her for a moment, speechless. Abigail had her own strange habit to say everything in an extremely serious way, but after five years of knowing each other Katerina understood that it was only a way to hide what she was really thinking, or maybe to mask a peculiar sense of humor. Anyway, she always found quite difficult to determine if the girl was joking or not.

Overlooking the not-so-much flattering comments about her skin and eyes, she thanked her and together they walked towards the Infirmary.

Their way was packed by a thick crowd of second-years, but when they reached their destination they found out that the Infirmary was empty.

"Madam Wainscott?", called Katerina, but the chubby nurse was nowhere to be seen. When she turned to suggest her friend to go back, she realized that she wasn't at her side anymore. She moved her gaze upon the white empty beds, on the tall wardrobes against the walls and at last on the deep end of the room, where Abigail was walking with rapid paces. In front of her there were two dividing curtains. Katerina saw her blonde head pull aside the curtains and carefully peek behind, and then turn again towards her.

"Kat!", called excitedly the girl. "Look!"

Katerina, who was already approaching her, stepped by her side and glanced at what her friend was pointing at.

In front of them there were three parallel beds, disposed one near the other. On the beds lay still three dark figures, completely covered by blankets. That sight made her slightly sick: she knew it wasn't like that, but it seemed like someone had brought there three dead bodies and then forgot about them.

"The petrified students," she whispered. In the meanwhile Abigail extended a hand and knocked with decision on what seemed to be the foot of the nearest student, trying to test its solidity. Not happy, she moved forward and pulled down the blankets in order to uncover the faces of two kids, one after the other.

Feeling a sense of discomfort, Katerina stared at their bodies: they looked more like statues than real people. There was something strange about their faces, however.

"Damn, they really look as if made of stone," Abigail serenely affirmed, mirroring her thoughts.

"Abigail, look at their faces," pointed out Katerina. "Don't you think there is something wrong with them? We were told the sickness hits all of the sudden, but then why do Hammond and Finnigan seem almost terrified? They are not simply afraid or worried, look: they rather seem scared to death."

Abigail considered the disturbing expressions on their faces, and then uncovered also the third victim.

Her face was surely not relaxed, but showed what could be described at most as vague surprise, surely not terror. Weird.

Suddenly they heard the sounds of someone approaching, and they hurried to put the blankets like they had found them a few minutes before. When the nurse came in, Katerina tried her best to hide the guilty look on her face and promptly asked for the painkilling potion she needed.

While they were heading to the Potions classroom, Abigail and Katerina talked about what they had just seen.

"The Syndrome could cause the victim to hallucinate. Or maybe it slowly takes over, giving time to realize that something is wrong. At least it would explain their terrified expressions."

"Or maybe it's not a sickness at all," conjectured Katerina. Abigail didn't say anything.

They reached the classroom a couple of seconds before Professor Slughorn, who announced, to the extreme dismay of the Ravenclaws and Slytherins, that he had prepared a 'friendly' pop quiz to test their knowledge on the Strengthening Potion. Mentally thanking Merlin for her disappeared migraine, Katerina began to dispose pens and inkpot on her desk.

Katerina Farley, Ravenclaw, she gingerly wrote on the border of the sheet. Theory of Potions, March the 5th, 1943.

Library, again. Section of History of Magic, again. It was nearly the same scene as the night before, with a slight difference: the girl now wasn't avidly reading one of her books, but was dozing with her head resting on the wall. No one could sleep in that position and then wake up not wishing to tear off their neck, but, well, he surely wouldn't go and wake her up.

She was no Lauren nor Bonnie: her name was Katerina, as he had discovered that day following her around the castle. She was a fifth-year Ravenclaw, and in the morning she had attended Aritmancy, Potions and Charms, with a small deviation to the Infirmary. Clearly he lacked the means to spy on her during her lessons, but thanks to a useful little Locating Charm he had cast on her the night before he was able to find her wherever she went after each lesson.

Before dinner had been in the Library to write a essay; after dinner she had come back to the Library – original, really – but had fallen asleep right away. It was understandable that she was so tired, after what had happened the night before – not that she could remember any of it, of course.

For the umpteenth time, the Prefect told himself that it wasn't strictly necessary to look after her. But it was better that way.

There was still half an hour before curfew; in the Library a couple of dozens of students were still studying, and he was sitting at a table reading his notes on the Transfigurations lesson of that day, glancing every once in a while at the sleeping girl.

He was absorbed by a particularly nasty theorem on the Transmuting Spells, when he absent-mindedly happened to get a glimpse of the History section. What he saw, or actually didn't see, made him jump on his chair.

The girl was not there.

Cursing his distraction, the Prefect briefly wandered around to make sure she wasn't in the surroundings. Back to the table, he hastily threw together all of his stuff in the bag and rushed out of the Library.

"Point me," he whispered when he reached the first fork. The wand suggested to go upstairs. Surely the girl was too sleepy to study and decided to go back to her Common Room, he thought while he increased his pace. Nothing to worry about. But he needed to see her, to be sure, and then he could go back to the dungeons and stop thinking about it.

Maybe she saw him in the Library? Did she recognize him? No, it was impossible.

Following the instructions of his wand, he rapidly walked along an empty corridor on the third floor. The girl could not be far. Or maybe she could? How much time had passed while he was distracted by his readings? He really couldn't say.

He turned a corner and suddenly saw in front of him something that froze the blood in his veins.

The corridor was slightly dark. A few torches on the wall sketched shaking shadows on the barren stone; there were no paintings. It was the wing were the old Potions Lab was, he absent-mindedly registered; the old Lab that had not been used since the last Potions Mistress decided to move to the Dungeons. That place was abandoned; there were only empty classrooms.

And in the middle of the corridor the girl laid on the floor, motionless and wide-eyed, a cheek on the cold ground. A horrible gash ruined her face, forming a bloody wound on her neck. Her long hair surrounded her head like a halo. Her sweater was ripped in two, and the white shirt below showed an increasing red stain. The blood was everywhere: under her body, on the walls, on the window a few meters away. Vague trails of water could be seen on the floor.

Even as far as he was standing, the Prefect knew with absolute certainty that Katerina's heart was no longer beating.