Canterlot Town. A city whose nights were protected by a mysterious girl wearing a purple spandex suit, a flowing blue cape and a stylish hat. No matter how quiet or secretive, the girl called The Mysterious Maiden Do Well was always there to thwart whatever evil deed was taking place - and that's why she had to be extra careful. She pulled a metallic sphere and a remote control from her tool belt and, after taking a deep breath, threw the sphere at the glass window of the museum. The glass shattered, allowing the sphere to enter the building.

Once it was inside, she pressed a button on the remote, activating the sphere, which was a concealed EMP grenade. The electromagnetic pulse it caused wasn't powerful enough to permanently damage the security system of the museum, only deactivate it for exactly 3 minutes and 6 seconds - she had to act fast.

She jumped through the shattered window and ran straight to her target: a heart shaped pink diamond necklace. She removed the glass box that covered the pricey accessory and reached for it, but a second hand wearing a dark blue glove grabbed her wrist before she could claim her spoils.

Sonata was closer to the museum than ther other Maidens. The sound of the glass window shattering attracted her straight to the crime scene just in time for her to witness the suspicious-looking person going through the improvised entrance. Following her inside, she could take a better look at the burglar: she was a girl wearing a dark purple spandex suit that covered her entire body, light blue gloves, boots, utility belt and helmet. She was reaching for an expensive-looking necklace, so Sonata seized her immediately.

She grabbed the woman's wrist and was about to apply a wristlock when the thief countered with a palm heel strike to Sonata's nose. Taken by surprised, she clutched her nose in pain, giving the burglar an opportunity to run away with the pink diamond necklace. The Maiden, trying to ignore the pain, chased her.

Despite not being as fit as her teammates, Sonata was the second fastest of the team, losing only to Sunset Shimmer. She managed to block the other girl's path, who tried to unblock it with a jump kick, but Sonata managed to avoid it and grab her by the ankle, making the burglar fall flat on her butt.

The watch on the girl's wrist beeped. 3 minutes and 6 seconds had passed. The alarm sounded immediately. The sound was too loud and too close to Sonata, enough to be painful for her siren hearing, so she let go of the burglar's ankle to cover her ears. Not wanting to waste the chance, the masked girl jumped out of the window, soon followed by the Maiden. Sonata tried to chase her, but her head was still a little fuzzy due to the loud noise, so she was unable to focus her vision or keep her balance. Sonata Dusk then fell to her knees.

"And I totally had her, but then the alarm suddenly turned itself on. It was so, so, SO loud that it was hurting my head, so she escaped. I tried to follow her, but my head was hurting so bad that I just couldn't." Sonata sighed as she finished telling her teammates the events that transpired in the museum. "I'm sorry I let her go..."

"It's ok, Sonata, it wasn't your fault!" Sunset said as she placed her hand on Sonata's shoulder. "Don't worry, we'll do our best to catch that thief, you don't have to worry!"

"For realzies?"

"Yes, Sonata! For realzies." Sunset turned around to look at Adagio, who was already checking the footage of the street cameras. "Any luck?"

Adagio shook her head slightly as she took a sip of coffee. "Whoever that person is, she must be a pro. I mean, other than two seconds of her jumping out the museum window, I got nothing!"

"Well, two seconds is better than nothing. Let me see it!"

Adagio pressed "play", showing in slow motion exactly what happened after the alarm system of the museum was back online: Sonata let go of the thief's ankle and covered her ears, and the thief immediately jumped out of the window. Adagio paused in the exact frame of the girl about to jump, which allowed them to take a good look at the outfit she was wearing; dark purple spandex suit, light blue boots, gloves, utility belt and helmet.

"Hm..." Aria approached her face to the screen as she rubbed her chin.

"Something wrong, Aria?" Trixie asked.

"I can't quite put my finger on it, but that person... No, that helmet! I'm almost entirely sure that I've seen it before somewhere!" Aria said. "Where have I seen her before?"

"Now that you mentioned it, I think it looks oddly familiar... Well, only one way to find out!" Adagio said as she cracked her nuckles. "Research!"

"So, you're staying over?" Aria asked. Adagio nodded as she took another sip of her coffee. She shrugged, opened the door and exited Sunset's apartment, followed by Trixie and Sonata.

"Goodnight!" Sonata said with a bright smile as she closed the door.

"So, about my suggestion of the five of us sharing one apartment. What do you think of that?" Sunset asked as she wore her pajamas. "The conveniences outweigh the inconveniences, and I think we could--"

"Look, can we talk about that tomorrow, Sunset?" Adagio interrupted. "I really need to concentrate over here!"

Sunset sighed. "Just don't pull another all-nighter, Adagio. It's a school night." she said as she jumped in bed. "But do not hesitate to wake me up if you find something!"

"Sure thing!"

In the morning, Sunset sat up and stretched her arms, but when she looked at the guest bed, it looked exactly the same as last night. She looked at the computer and saw Adagio resting her face on top of the keyboard, sound asleep. Sunset shook her head, got up and gently placed her hand on Adagio's shoulder, a gesture that woke her up immediately!

"Huh? Wha?" she frantically looked left and right, accidently bumping the mouse with the side of her hand. The screensaver was turned off, revealing the last thing the siren found before passing out: a mugshot of Vice Principal Luna.

"What the...? What is this?" Sunset asked, rubbing her eyes to make sure she wasn't seeing things.

After rubbing her eyes and yawning, Adagio looked at the website's name. "Criminal Records Database."

"Wait, does that mean Vice Principal Luna is a wanted criminal?"

"Was, actually! She was already arrested and served her sentence."

"Then what was her crime?"

"Breaking and entering into places wearing a disguise and stealing valuable objects!"

"Wait! You mean like...?"

Adagio zoomed in a picture of Vice Principal Luna wearing said disguise: a black spandex suit with dark purple gloves, boots, utility belt and a light blue helmet.

Sunset gasped, pointing at the screen. "It's the same person from last night!"

"A little change of wardrobe, but the design and definitely the helmet are still the same."

The sound of the door being practically kicked open startled both of them. Trixie entered the apartment and shoved a newspaper on Sunset Shimmer's face.

"Look at this!" Trixie commanded.

Sunset took the newspaper in her own hands and read the article.

"'Nightmare Moon Watches Sunrise From Behind The Bars'." she looked at Trixie, who motioned for her to keep reading, which she did in silence. "Oh, so Nightmare Moon is the name they gave that thief from last-- Vice Principal Luna was arrested?!"

Trixie nodded. "Apparently she is the prime suspect of stealing the pink diamond from the museum last night."

"So this is why Aria and I thought she looked familiar." Adagio said. "We met her before!"

"You did? When? And how?"

"It happened a few years ago. She broke into our apartment and tried to steal our necklaces! I'll admit, that took guts!"

"And what happened after that?"

"Aria and Sonata held her down as we sang her a little song. When the effect of our spell wore off, she was already found guilty in court."

"Whoa!"

"Hey, we loved those necklaces back then. We wanted to make sure she would pay for trying to take them from us."

"So, what do we do now? The culprit was caught, mission accomplished, right?"

"Something smells fishy, though!" Sonata, who was standing behind Trixie, said, startling her.

"When did she got here?" Trixie asked, pressing her hand to her chest to make sure her heart wouldn't jump out of her ribcage.

"What do you mean, 'smells fishy'?" Adagio asked.

"Remember when we met Nightmare Moon back then?" she asked. Adagio nodded. "How tall was she?"

"Pretty t-- Oh, I see what you mean!"

"What? What am I missing here?" Trixie asked.

"Vice Principal Luna is, like, super tall!" Sonata said. "But this girl I met last night... She wasn't! Not even close!"

"So you think someone is trying to frame her?" Sunset asked, looking at the picture of the Nightmare Moon from years ago and the screenshot of the Nightmare Moon from last night.

"It's a possibility."

"Alright, then!" Sunset said as she grabbed her black leather jacket.

"Where are you going?"

"Detention center! I need to speak to Vice Principal Luna."

Detention center. Visitor's room. The room was divided in half by a wall with a big glass window. One side of the room, which had an alert guard and a watchful camera, led to the holding cells where the detainees waiting for trial were kept. The other side of the room led back to the Criminal Affairs Department, where the police officers did most of their paperwork. Sunset Shimmer entered the visitor's room through the door that led back to the Criminal Affairs Dept. Vice Principal Luna was already there, talking to another person.

"Principal Celestia?" Sunset Shimmer called.

"Sunset Shimmer. I wasn't expecting to see you here!" Principal Celestia said.

"I wanted to talk to Vice Principal Luna."

"Just Luna is fine." the detainee said. "We're not in school. And I don't think I'll be going back for a while. Anyway, what do you want to talk about?"

"About last night--"

"I did it!" Luna said, interrupting her. "I broke into that museum and stole that brooch. It was all me, and only me!"

"You... What?"

Principal Celestia sighed. "Luna, stop this. I know you're innocent!"

"Do you have any proof of that? Huh?"

"Everyone is innocent until proven guilty."

"Well, and I say that video footage is proof enough! Decisive evidence! Just leave me to rot and--"

"It was a necklace that was stolen, not a brooch!" Sunset Shimmer corrected her.

"I-I just got confused! It was too dark to--"

"You're doing this to protect her, aren't you?"

Luna immediately stopped talking and bit her lower lip. She then looked away from her sister.

"Wh-Who? I d-don't know what you're talking about."

"You don't need to lie to me, Luna. I already know about you two!"

"How... How did you--?"

"That night after you got out of prison. You thought I was asleep, but I followed you!"

"What are you two talking about?" Sunset Shimmer interjected.

Luna looked at Sunset Shimmer and then at her sister, who nodded slightly.

"You won't leave me alone until I tell you everything about her, will you?" Principal Celestia just kept staring at her sister with a neutral expression.

Luna sighed and looked at Sunset Shimmer. "Years ago, I--"

"Used to be a thief called Nightmare Moon, right?"

"I see that you did your homework! Yes, I used to be... That! It was just my rebel teenage phase. Since we were kids, my sister was always the pride of the family! She was pretty, her grades were perfect, she was well-behaved, polite, could sing like an angel and even play violin! Daddy's little princess! I was just... Not. I, too, wanted some attention. I, too, wanted to be praised! But no matter how much I tried, I could never be as good as Princess Celestia!

"That's when I decided that I would be worse than her. I started breaking things, teasing other kids, I don't even remember how many hours I spent in detention! Daddy's face of disappointment was always painful to look at, but it was the only moment when he payed any attention to me. That kept going until I couldn't take it any more and ran away from home!

"What a stupid kid I was, huh? Running away because of jealously? I tried finding a job, but my personality was hard to deal with. I saw no other option but turn to crime. I started small; picking pockets, shoplifting... After a while I decided to sew a costume to hide myself in. Partially to not be recognized, but mostly in shame. The helmet was the first truly valuable artifact I stole, so I kept it to myself as a trophy! Before long, I was breaking and entering places and selling my loot to a pawn shop owned by two shady brothers.

"One cold night, after another successful heist, I returned to my hideout. And that's when I met her; a little girl wearing tattered rags seeking shelter from the cold. She was filthy, cold and hungry. I couldn't bring myself to just kick her out, so I offered her a warm meal and a hot shower. I learned her story soon after: her parents were poor and coudn't afford to feed another mouth, so they abandoned her on the streets. I felt truly sorry for the little girl, so I 'adopted' her.

"I taught her everything I knew, and together we learned many new things, but I never allowed her to acompany me! And then I got arrested. I don't remember exactly what happened, my memories of that night are a little cloudy, but I'll never forget daddy's face when I was found guilty. It was like his disappointed face, but much worse! I cried as I was taken away, but not because of his expression; I cried because my daughter was alone in the streets again.

"When I served my time, Celestia was there to pick me up and take me to her home. I was grateful for that, but I had to see her again! When Celestia fell asleep - or, rather, when I thought she was asleep - I ran straight to my hideout. Words can't describe the joy I felt when I found her there, all grown up, waiting for me! While I sat in my prison cell, waiting for my time to leave, she was busy honing her skills. My time in jail was what I needed to learn that the criminal path I followed was not the correct path and tried to teach her the same, but she wouldn't listen to me. She yelled at me, angry that I was abandoning what had united us, and ran. I went back there several times, but she never returned."

After listening to her sister's tale very closely, Celestia asked one last question:

"You never told us her name. What was it?"

Luna bit her lip again. "No! You want to arrest her to get me out of here, no? I won't let you take her! She might not be perfect, but she is still my daughter!"

"Luna, think about it!" Principal Celestia said. "If we get to her first, we can put her in the right path, save her. But if the police gets to her first, they will just throw her here, no questions asked, and she will just get worse. Which option do you think is best?"

Luna's eyes shifted from Celestia to Sunset, and then back to Celestia.

"Please, trust us, Luna!" Sunset Shimmer pleaded.

Luna sighed. "She never told me, actually! Every time I asked, she would say it was the name her biological parents gave her, and so she hated it. So I came up with a new name for her."

Sunset approached the glass, to make sure to listen to the name as clearly as possible.

"Her name is Tantabus!"

Sunset Shimmer and Principal Celestia left the detention center side by side. Before they could part ways, Celestia grabbed Sunset by the shoulders.

"I need your help, Sunset."

"Uh, with what?"

"Luna! I know she cares a lot about that girl, so I need you! Forgive me if I sound rude, but you also followed a dark path in the past, did you not?"

"Well, I--"

"You know how it feels, so you must know what we need to do to save Tantabus, correct?"

"Y-Yes, I--"

"We need to find her before the police does. Set her straight before it's too late. If we can somehow make her confess her crimes, we will not only save Luna, but also find a way to get her a lighter sentence!"

"Sounds like a plan, I--"

"I know this is too much to ask, but I would be very grateful if you and your friends could help me look for her. Can you do that?"

"I--"

"Can you?"

"I... I'll do my best, Principal Celestia!"

"Thank you so much, Sunset Shimmer. You truly are a wonderful person! But be careful, though. We can't let anyone get to her first. Especially the Maiden Do Well!"

"W-Why not the Maiden?"

"We all know how she works. She would just knock her out, call the police and leave. Do you think this will help the girl in any way?"

"W-Well..."

"I must go back to school now! Do you want a ride home so you can get ready for class?"

"N-No, I'm good."

"Fine, then. Goodbye, Sunset Shimmer. And thank you!"

"Anytime."

Sunset Shimmer turned around and walked back home as Principal Celestia got in her car and drove away.

"There you are!" Aria said when Sunset Shimmer arrived. "What took you so long?"

"Girls, we need to talk!"

Author's Notes:

Our favorite heroine and her secret identities are back!

And before you ask, the thief girl couldn't use a stronger EMP device because it would affect other buildings in the area, and that would attract the authorities like blood attracts sharks.