Sirius wandered into Grimmauld Place's kitchen in search of a late night snack, but instead discovered a young girl seated at the table whom he had never seen before. He stopped in his tracks just inside the kitchen door the second he spotted her, pulling his wand out, but it was too late. The door behind him slammed shut as the girl looked up, locking eyes with him, a small smirk playing on her lips. "That was much easier than expected," she said, her voice light and delicate, almost sweet.
Sirius tilted his head, curious, his wand still trained on her. "Who are you?" he asked, never taking his eyes off her as she stood.
"You know who I am," she replied, stepping around the table slowly, getting closer to Sirius with every step. "You might not recognize me after all this time, but you know me."
"Give me a name, and I might recognize you better," he countered. "And I'd suggest staying right where you are if you don't want to take the risk of being cursed, little girl."
She stopped right across from him, the table no longer between them. "Fine," she said quietly. "I won't come any closer. But you can't tell me that I don't look at least a little familiar."
Sirius looked closer at her face, at her shining blue eyes framed by long, dark brown curls. He shook his head. "Sorry, I don't know. You remind me a little of someone, but I'm not sure who."
The two's attention suddenly turned to the open door at the other end of the room, from which they heard footsteps. Just as Lupin came into view and spotted the two, the girl waved her wand and slammed that door shut as well, locking Lupin out. Lupin banged on the door, yelling for Sirius to let him in. Sirius quickly sent a Stunning Charm her way, but she blocked it easily. "Who are you?" he demanded again.
She sighed, clearly frustrated. Lupin pounded on the door again, much louder this time, startling the young girl and making her jump. As Lupin finally got the door unlocked, she said, "Isabelle. My name is Isabelle," disapparating out of the room as the door flew open and Lupin rushed in.
"Sirius! What was that all about? What are you doing? Who was that?" Lupin demanded, rather irritated with his friend.
Sirius continued staring at the spot where the girl had disappeared for another long moment before responding, "She claimed to be Isabelle."
Lupin stared at his friend in shock. "That's not possible, Sirius."
"I'm well aware of that, Remus. But then again, you also said it wasn't possible that it was really Wormtail that Harry was seeing on the map, and yet it was," Sirius said quietly.
"Yes, I know, but Sirius, you watched her die in that fire. There's absolutely no way it's possible."
"She looked just like her, Remus. I saw it as soon as she said the name. She's about the right age to be Isabelle…"
"But Isabelle has been dead for 16 years, Sirius."
"I know that, Remus!" Sirius snapped. "I didn't say that it was her, only that she claimed to be, and it almost seems possible. Who knows what else she would have said or done if you hadn't shown up when you did. She may have had more proof than simply knowing the name."
Remus sighed. "All right, I'm sorry. Just be careful, Padfoot."
The next morning at breakfast, Sirius moved to sit by the Weasley twins instead of sitting in his usual spot by Harry. "Fred, George," he said quietly. "Do either of you know a girl in your year named Isabelle?"
Every adult in the kitchen immediately fell silent the second the name crossed his lips. Molly turned from the stove. "Sirius, what's this about?"
Sirius responded without even turning around. "Simply curious, Molly. So, how 'bout it boys?"
"Sirius," Lupin said quietly, a warning tone to his voice.
George grinned mischievously. "Actually, now that you mention it, there is. Isabelle Guinn. Ravenclaw. Fred's been trying to flirt with her for the last two years, but he's gotten absolutely no where."
"George!" Fred glared at his brother. "Wasn't necessary to tell them that."
"No, but it was fun," George said laughing.
"What does she look like?" Sirius asked eagerly.
Fred responded quickly, "Dark curls, blue eyes, pretty face, short, slim, really cute…"
"Sirius, what are you playing at?" Molly asked.
Sirius shook his head. "Nothing."
It was almost one in the morning before Sirius returned to his room from taking care of the hippogriff hidden upstairs. As he closed the bedroom door, a voice behind him said a quiet "Hello." He spun around immediately, wand out and ready to defend himself, only to find himself face to face once more with the girl claiming to be Isabelle. He sighed in exasperation, but never lowered his wand. "How do you keep getting in here? This house is protected by the Fidelius Charm; the Secret Keeper never brought you here."
"Actually he did, he just didn't know it," she said quietly. "Pretending to be Tonks wasn't that difficult, as often as she changes her appearance."
She sat down on the bed, setting her wand down beside her. Sirius instantly summoned the wand, and it flew into his hand before she could recognize her mistake. "Lesson number one about war time: never set your wand down when you don't know if you can trust the person you're with. It's easily stolen if you do, leaving you defenseless. Which is exactly what you are right now. I have no reason to believe that you're really who you say you are, so why would I not take your wand when the opportunity presents itself?"
She replied, "I don't mind surrendering my wand. I trust you won't hurt me."
"Yes, you trust that because you are young and foolish."
"Or I trust that because I know that you know deep down that I'm telling the truth."
"Isabelle's dead. I've been dealing with the grief from that fact for the last sixteen years. She's not going to just reappear as a teenager because I want her to. Which is why I think you're really someone working for Voldemort, trying to get me to let my guard down and get close to me in order to get to Harry. So why don't you just tell me who you really are and what you're really doing here, Miss Guinn? That is your name, isn't it?"
She stared at him with wide eyes. "Yes, that is my name. But I swear, I'm not lying. I'm really her. I'm really that Isabelle. I can prove it."
Sirius glared at her suspiciously. "What kind of proof?"
Suddenly, there was a knock on the door. "Sirius?" Harry's voice floated through the door.
Sirius turned toward the door, but reacted instinctively when he felt the girl's wand being pulled out of his hand. He turned suddenly and grabbed the girl's arm and shoved her rather roughly against the door. The girl's eyes were filled with fear, but her hand never left her wand, which he still had a firm grip on. "Don't think you'll get this back so easily, little girl," he said, a harsh edge to his voice. "What do you need, Harry?" he called through the door.
It was a moment before Harry answered. "Um, well, I just wanted to know if we could talk for a few minutes."
Sirius thought for a few moments, watching the girl in front of him. "Yeah, Harry, we can talk," he responded slowly. "I just have to finish dealing with something first."
Out of nowhere, Sirius felt a burning sensation run down his back. He hissed in pain, unintentionally loosening his grip on the girl and her wand. She wrenched the wand out of his hand and disapparated before he could stop her. Harry knocked again. Sirius opened the door, still hunched over in pain. "Sirius!" Harry exclaimed. "Are you all right? What happened?"
Sirius looked around his room for a moment, but the girl was gone. "Nothing, Harry. I'm fine. What did you need?"