Hogwarts had changed — really changed. The breakage of small, petty rules such as running in the corridors was punishable by means of the Cruciatus Curse. The Carrows loved the Cruciatus Curse.

Storm clouds seemed to hang over the school at all times, and although it never rained, there was an occasional crack of thunder and a gloomy atmosphere seeped inside the castle walls. Even Peeves had given up on causing mayhem, which was really saying something.

Katie barely spoke to anyone. She was not exactly on speaking terms with anyone in Slytherin, so she sat alone at meals and ate in silence, and she spent as little time as possible in her common room, instead choosing to do her homework in the library. The other students seemed to be giving her a wide berth — perhaps they were unsure if she really was a Death Eater or not.

She had Herbology and Charms classes with Neville, but other than this, she was alone in her classes. Sometimes Ginny and Neville would join her in the library, which was exactly where the trio were when a sudden realisation struck Katie.

"Where's Luna?" she asked.

In perfect synchronisation, Ginny and Neville's faces paled, and they shared a nervous look. Then, Ginny gulped harshly and said, her voice hoarse, "We don't know."

Katie blinked, bemused. "What do you mean?"

"She's just disappeared," Neville said. "She never came back after Christmas."

"Maybe she just chose to stay home?" Katie suggested. "I mean, if I had a choice, I wouldn't be here, it's horrible."

Ginny shook her head. "We don't have a choice. Everyone has to come to school. And what do you mean, if you had a choice? You skipped the first term, why come back now?"

Katie's mouth went dry. She realised that she had said too much. Clearing her throat and scratching behind her ear, she mumbled, "It doesn't matter."

Ginny eyed her sceptically but she could see how uncomfortable she was so she let the subject drop. Ginny then reached into her bag, pulled out a gleaming, golden Galleon and slid it across the table to Katie, who slammed her hand down on top of it before it could slide onto the floor.

Her confused eyes danced between Ginny and the Galleon. She had just opened her mouth to ask why Ginny had spontaneously given her money when Ginny answered the unspoken question for her.

"I'm taking it you don't still have your DA coin on you?" Ginny said. Katie's eyes widened and she lifted up the fake Galleon to examine it in the light.

"This isn't — you haven't..." she gasped.

Neville smirked. "Oh yes we have. You've seen the way Amycus teaches — it's not Defence Against the Dark Arts anymore, it's just the Dark Arts."

"We all know there's a fight coming," Ginny added gravely. "We all need to be prepared when it happens. So, will you rejoin the DA?"

Katie knew Ginny and Neville were taking a great risk by reforming Dumbledore's Army. If they were caught, they probably would have been tortured into madness, and as Katie stared at their hard, determined faces, she did not think she had ever admired two people more.

"I'm in." Katie said, pocketing her Galleon.

***

The area that the Room of Requirement provided for DA training was exactly the same as Katie remembered. One wall was entirely obscured by shelves hosting huge, old and dusty books. A pile of silk cushions sat in a basket in the corner, and a fire glittered in the mantle at the far end, reflecting in the many mirrors.

Katie saw some familiar faces: Seamus Finnigan, Colin and Dennis Creevey, Lavender Brown, Hannah Abbott, the Patil sisters, along with many more. As expected, they all stared at Katie as she entered, as opposed to Neville and Ginny, who smiled.

"What's she doing here?" Lavender pointed at Katie, who was reminded instantly of the time that Ron was poisoned and Lavender arrived in the hospital wing to find Hermione at Ron's side.

"She wanted to rejoin." Ginny said calmly, but she did shoot Lavender a discreet, nasty look.

"Isn't she a Death Eater?" Padma Patil cut in loudly. A few people hummed in agreement. "How do we know You-Know-Who hasn't sent her here as a spy?"

Katie shivered because she knew that was the reason she had been sent back to Hogwarts. Voldemort wanted her to help Snape take down the school from the inside but, of course, that was not her intention.

Ginny's eyes narrowed. "Now you listen here, Patil—"

"It's OK, Gin," Katie said, then she looked straight at Padma and rolled up her sleeves. A few people winced. "See? No Dark Mark."

"Where were you this whole time, then?" Parvati Patil demanded.

"That's none of your business." Katie shot her down quickly.

"Exactly," Neville said and Katie smiled gratefully at him. "Now, we've got a lot of spells to cover, so let's stop interrogating Katie and get to work."

They broke into pairs to practice disarming to refresh their memories. Ginny grabbed Katie's arm and pulled her off to the side.

"You went on that secret mission with Ron, Harry and Hermione, didn't you?" Ginny asked conversationally as she and Katie took it in turns disarming each other.

Katie nodded. "Yeah."

"Can I ask — where did you go? What was the mission?"

Katie stopped muttering the incantation and frowned, her shoulders slumping. She wanted to tell Ginny everything, she really did — from every last detail about the mission to the truth about Katie's parentage, but she knew that Dumbledore wanted no one else to know about the Horcruxes, and she could not handle the look on Ginny's face if she were to let slip that Voldemort was her father.

"And why did you leave them?" Ginny asked, an undertone of bitterness to her voice. "Why did you come back to Hogwarts?"

Katie's mouth went dry. Her brain worked hard to rapidly try and come up with a believable excuse, but she decided to just tell the truth — most of it, at least.

"You-Know-Who showed me this vision of him torturing Draco so I went to Malfoy Manor to rescue him." Katie explained.

Ginny quirked an eyebrow. "But Malfoy was here."

Katie sighed and nodded. "It was a trap. Voldemort wanted me to join him so he lured me to Malfoy Manor and kept me locked there."

"How did you escape?" Ginny gasped.

Katie wanted to tell Ginny that she didn't escape, that Voldemort had let her go under the order that she return to Hogwarts and help Severus Snape corrupt the school, but she caught her tongue.

"Lucky break," Katie lied smoothly. "Christmas morning, when Bellatrix was coming in the front door, I made a run for it."

Katie wasn't entirely sure that Ginny believed her, but was relieved when the Gryffindor let it go, giving Katie one last, sceptical look.

***

It worried Katie how well she was performing in Dark Arts class. She told herself that it was just because of the training she had done with Bellatrix, but she knew, deep down, that this was not true. She was mastering extremely intricate Dark spells much quicker than the rest of her classmates, and this did not go unnoticed by them. They were all growing more and more suspicious of Katie by the day.

For the first two weeks of term, Katerina Blair was the talk of Hogwarts School of Witchcraft and Wizardry. Why, in August, had she disappeared from the world without a trace? Had she been traveling with Harry Potter, Ron Weasley and Hermione Granger, who were also missing, and if so, why had she left them? Were the rumours that she had joined the Death Eaters true? Why was she so skilled in Dark magic? And, possibly the question that circulated most, why had she returned to Hogwarts so late into the school year?

No one made any effort to hide the fact that they were talking about Katie. Everywhere she went, people ducked their heads together and spoke in rushed whispers, shooting Katie nervous glances and sometimes glares.

It was the event that took place one gloomy Thursday afternoon in Dark Arts class that became the main story of the week.

Rain pummelled against the windows, rattling the panes and creating obscene amounts of noise. The wind howled outside as the heavy rainfall reduced the Quidditch pitch to a swamp. Upon her arrival back at Hogwarts, Katie discovered that Quidditch had been cancelled for the year, which greatly disheartened her because the sport had been the one thing that she was looking forward to when she was ordered to return to Hogwarts.

The Dark Arts classroom was cold and, every time Katie stepped inside, she was reminded of Snape's dungeon. Green flames flickered in their brackets, creating dull and eerie light. Jars full of parts of creatures sat in green and brown liquids on a shelf. Despite the chill in the room, Professor Carrow had apparently not thought to light the fire.

Entering the Dark Arts classroom always made Katie feel uneasy, but today she was met with a sight that sent a shiver down her spine. Ten first years had been lined up against the wall. They were visibly shaking and their faces were as white as snow. None of them dared to move from their positions against the wall.

Katie gulped. She had no idea why the first years were there, but she could tell by their expressions that it was for no good reason.

Katie took her usual seat next to Neville in the back of the classroom and done her best to avidly avoid looking at the trembling first years. She and Neville exchanged a fearful look.

Once everyone was seated and silent, Professor Carrow began to explain their lesson for the day.

"I'm sure you are all wondering why I have brought first years to your class today," Amycus began. There was a sinister undertone of triumph to his voice, making Katie grow more anxious by the second. "During our last lesson, on Tuesday, I taught you the incantation for the Cruciatus Curse. Today, you will be practicing... on the first years."

A wicked smile split across Professor Carrow's face and Katie felt her blood turn to ice. She had already known that the Carrows were evil — they were Death Eaters, after all, but this was truly twisted.

Pansy stepped up first. She was shaking from head to toe, but being selfish and all that, she would rather torture an innocent eleven year old child than receive a few cuts to her face. Drawing her wand, Pansy approached a small girl who looked very similar to her. She had short black hair and bright green eyes that were filled with terror.

Pansy pointed her wand at the first year and said, "Crucio!"

Katie turned away and shut her eyes as the first year's screams echoed through the room. A loud thud told her that the girl's knees had buckled and she was now on the floor. Pansy lifted the spell after only a few seconds and returned to her seat with praise from Amycus.

"Next," Professor Carrow's eyes scanned the room, landed on Neville and widened as he grinned evilly. "Longbottom."

Neville gulped. "No."

Professor Carrow's face welded into a hard scowl. "Excuse me?" he barked.

All fear in Neville's eyes was diminished and he sat upright in his chair, his shoulders pushed back and his chin held high.

"I said, no."

In a flash, Amycus slashed his wand through the air and Neville yelped in pain. Three deep gashes appeared on his face and blood spurted from the wounds. Katie felt queasy just looking at him.

"Here..." Katie plunged her hand into her bag and pulled out a box of tissues, which she handed to Neville, who gave her a weak smile and started mopping up the blood on his face. Then, Katie turned and looked straight at Amycus. They glared at each other.

"Perhaps you would like to go next, Miss Blair?" Professor Carrow said darkly. Katie had been expecting this, but her stomach still twisted into knots when she was called upon.

As Katie rose steadily to her feet, Amycus plucked a first year from the crowd and brought him forward to the centre of the room. Katie could feel all the eyes of her classmates on her, awaiting what her next move would be.

Her shaking hand clutched her wand in her pocket, but she was not nearly as afraid as the boy before her. He had messy, sandy-coloured hair and striking blue eyes, which were swimming with tears. There was no colour in his cheeks. He looked like he was on the verge of passing out. With a horrible stabbing pain in her chest, Katie was reminded of Leo: small, helpless, afraid.

She raised her wand. The first year boy whimpered and instinctively stepped backwards.

Before anyone could react or understand what was happening, Katie rounded her wand on Amycus Carrow and bellowed, "Crucio!"

The entire class gasped, including the first years, as Professor Carrow was blasted backwards against the wall by the force of the spell and fell to the floor, screaming in agony. Katie held the spell for a few more seconds as Amycus writhed and thrashed around. She watched as justice was served at her own hands.

She could feel her wand vibrating with power. This was, perhaps, the strongest spell she had ever cast, fuelled by her anger that someone could be so cruel as to force teenagers to torture first years, and also fuelled by her hatred towards Voldemort and anyone who followed him.

Katie wasn't sure how much time had passed, but when she finally lifted the spell, Amycus was too weak to bring himself to his feet. He lay curled up on the floor, twitching and moaning, as the class was reduced to stunned silence.

Katie's chest heaved up and down as she panted. The realisation of what she had just done set in and she began to panic, but not before someone began to clap slowly.

She looked around. It was Seamus Finnigan — his eyes wide and his mouth hanging open. Slowly but surely, everyone began following his lead, and soon, the classroom was filled with applause and cheers. Katie looked down at Professor Carrow, who was still lying helplessly on the floor, then glanced to the door.

"Class dismissed!" she announced.

***

Katie had been eating dinner when the prefect found her. He was a tall boy with neat, dark brown hair and glittering brown eyes. He wore a pompous expression and looked at Katie as if she were the gunk on the underside of his shoe.

"The Headmaster wishes to see you." the prefect announced.

Katie was not at all shocked by this. By the time dinner rolled around, news of the event in Dark Arts class had spread like wildfire, and if Amycus hadn't gone running crying to Snape, the Headmaster surely knew by now.

The prefect escorted Katie to the seventh floor and gave the password to the stone gargoyle that guarded the Headmaster's office. The gargoyle sprung aside, revealing the spiral staircase, which lifted Katie up when she stepped onto it.

Snape's office was almost identical to Dumbledore's. The portraits of former Headmasters and Headmistresses snoozed in their portraits. However, whirring silver instruments that usually sat on tables throughout the room had been replaced by sinister objects that were probably reeking Dark magic. On one wall, shelves had been placed to hold all of Snape's disgusting potions and potions ingredients.

And there, at the top of the room, sat Severus Snape, perched in Albus Dumbledore's tall-backed, golden throne and leering at the Slytherin girl before him. It was only now — with a pang of sadness — that Katie noticed the portrait of the sleeping Dumbledore hanging behind his desk.

"Katerina Blair." Snape drawled, his voice filled with utmost loathing.

"Professor Snape," Katie walked forwards and took a seat without Snape asking her too, and she could tell by the narrowing of his eyes that he did not like this. "I've been wanting to see you, actually. I wanted to tell you how much I admire the wonderful changes you have made to this school."

Snape pursed his lips. "Don't get smart with me, Blair," he growled. "You're already in enough trouble as it is."

Katie shrugged nonchalantly, folded her arms and leaned back in her seat.

"You can't hurt me," she said. "Your master would have your head." She put a lot of emphasis on the word master.

"Indeed," Snape said slowly, and a smirk played at his thin lips. "I cannot hurt you. I can, however, hurt your friends."

Katie felt the blood drain from her face. Instantly, she moved to stand up, but Snape said, "Not so fast."

Glaring at him with a burning hatred, Katie lowered herself back into her seat. Her heart was beating fast and she anxiously tapped her feet against the floor, which seemed to annoy Snape, but he did not say anything.

Snape intertwined his hands and his eyes swept over Katie in a shrewd manner.

"Why have you returned to Hogwarts, Blair?" he asked.

"My father made me." Katerina responded easily. Snape's nostrils flared.

"But why?" he pressed.

Katie did not hide anything.

"He wants me to help you take control of the school, but you seem to be doing just fine on your own."

A deep, guttural growl erupted from the back of Snape's throat and, suddenly, as if someone had slapped her in the face, Katie understood why all of the Death Eaters seemed to despise her so much. She let out a chuckle as a smirk played at her lips.

"I always wondered why Bellatrix hated me so much, but now I understand," Katie said. Snape's eyes darkened. "You and your Death Eaters are all the same. You're jealous."

Snape's glare hardened. "I am jealous of no one."

"Sure you are," Katie fought back the smirk that was threatening to form on her face. "You've all been working for years to prove yourselves, to be named his most loyal servant. Then I show up out of nowhere, with absolutely no loyalty to him, and suddenly I'm his favourite and he cares about me more than he does any of you. I won't even join him and I'm still more important to him than you and any of the other Death Eaters."

Snape's eyes glittered maliciously, and Katie knew that, were she not Voldemort's child, she would probably be dead.

"This discussion is over, Blair." he spat venomously.

Feeling rather pleased with herself, Katie left Snape's office. It was only when she reached the hallway below that she remembered...

"I cannot hurt you. I can, however, hurt your friends."

"Ginny..." Katie whispered.

She took off at a sprint. She did not need to be given directions — she had a fair idea as to where Ginny was.

Five more minutes later, Katie threw open the door to Amycus Carrow's classroom. The professor was nowhere to be seen, but slumped at the wall, wiping blood from her face using her sleeve, was Ginny Weasley. She looked up, startled at the sound of the door banging open, and Katie could see that her eyes were red and puffy and her freckled cheeks were tear stained.

Katie felt like someone had just hit her across the head with a bag of bricks. She rushed forward and dropped to her knees beside Ginny.

"Merlin's beard, Gin..." she gasped, pulling tissues from her pocket and getting to work on helping Ginny clean up the blood. "I'm so sorry, this is all my fault."

Ginny, however, grinned at her. The smile was crooked and Ginny seemed quite disorientated, but she exclaimed, "Are you kidding? Neville told me about what you did. That's awesome, Katie!"

But Katie frowned. As she looked at her friend, whose face was covered in gashes that were still slowly oozing blood, she wasn't sure she agreed that what she had done was awesome.