They searched together. There were a pile of papers on the table, each one covered in multiple highlights, the yellows, pinks and greens catching Marinette's attention. She flicked through them. They were profiles on each of the missing elves. There were notes scribbled in the margins. She touched one with her finger, feeling the indentation of the hastily scribbled word. Single.

Was Alya so interested in their relationship status? Or did it mean something else?

It took a moment for Marinette to realise that these pages were photocopies of the files they kept on each elf – names, ages, home towns and what they had asked for Santa as children.

All the elves at the North Pole were originally from the 'real world' that one way or another had found their way here. Anyone who reached adulthood and still believed could find the North Pole. Sometimes they stayed for one Christmas and left again. Most stayed forever, made families here. Some had children, some didn't. Except for the magic, it really wasn't that different from the rest of the world. And even the rest of the world had magic for those who believed.

Somehow, Alya had got hold of the records and copied them. It was hardly surprising, Alya being Alya, but even so they were kept under lock and key in the armoury.

It was scary what Alya could accomplish when she put her mind to it.

Page after page, each annotated with details of their personal circumstances, what they ate the day of their disappearance, who their friends were, even how happy they seemed to be.

"Marinette! I've found something."

Adrien stood up from behind the table.

"Here." And he propped himself on the edge of the table next to her chair, putting a spiral notebook in front of her. "She must have dropped it," he said as she opened the cover, reading Alya's familiar handwriting. "I found it wedged just under the filing cabinet over there."

Marinette nodded but didn't reply, already absorbed in what Alya had written.

Underlined on the first page in large letters were the words 'follow the butterflies'.

"Follow the butterflies..." she whispered.

"What was that?" Adrien asked, leaning over to look at the notebook.

"Follow the butterflies," she repeated, looking up at him quizzically. "What does that mean?"

"At least it wasn't 'follow the spiders'." He shuddered. "Surely she wouldn't have put something so cryptic and nothing else?"

Marinette turned the page.

"Mm, that's all she said about butterflies. But she has put a few theories about the disappearances."

Adrien got up from the table and walked over to the wall of pictures again, inspecting them closer.

"She's written here that she thinks their mood might have been a factor. Everyone who was taken had had a bad day. Maybe the Krampus used them being upset to lure them away? But I still don't understand how - "

"Butterflies," Adrien muttered now, his face getting closer to the pictures. "There's something... I'm not sure..."

"What is it, Adrien?" Marinette stood too, coming to stand by his side.

"There's just," - he pointed to one picture and another - "can you see?"

She squinted.

"I'm not sure."

"Do you think we could look at the CCTV footage?"

Marinette nodded. "Let's go and see Max."

"Really, Marinette, I'm very busy at the moment. I hardly have time to go trawling through CCTV for hours on end."

She wrung her hands together.

"Please, Max, there's no one else I can ask and I think if we can see the disappearances then we might be able to solve this."

Max frowned but rolled his chair over to the bank of monitors.

"Alright, but this is the last time. Can you give me the exact time, date and GPS coordinates?" He looked expectantly up at her, his fingers poised over the keyboard.

"Oh, ah, um... yeah." She patted at her pockets. Dates and times were definitely in Alya's dropped notebook.

"Fifth of December, three forty-one PM," Adrien spoke up when Marinette couldn't find it. She looked up and he had the book in hand. "You left it on the table, I thought we might need it. That was the first disappearance."

"Alright. And where?"

"Ah, um." He glanced back down. "The corridor west of the mess hall?"

"Hmm," Max said, clicking the mouse and pressing keys. The monitor in front of them flashed through some images until it landed on Juleka's face. It was the exact moment she disappeared.

"Wind it back a bit please, Max."

He complied, taking it back to when she first stood still, her head hanging. She looked... defeated, her shoulders slumped, her hair a veil covering most of her face. Marinette could still see the down turn of her mouth.

Max hit play.

It was hard to tell, the image was in black and white, but there was something across her face.

They went though each of the victims and it was the same for all of them. When it came to Nathanael, he was closer to the camera, his face pointed towards it. More clearly they could see the shape.

"A butterfly, right?" Adrien asked, leaning closer to the screen.

Marinette leaned closer too.

"I... think so?"

She sat back in her chair.

"Is this really what Alya meant though? How can we follow that?"

Adrien tapped his chin.

"Can we see if we can find Alya's disappearance? Maybe there will be some kind of clue?"

She nodded, her mouth twisting.

"I'm not sure when she disappeared though. It must have been before I sent the text, she would have seen it otherwise, for sure. She was waiting to hear about her sister, she was so worried about the attack. Max, can you check from just after the alarm going off yesterday?"

Max gave a curt nod. "Where are we looking?"

"Room three in the radio building."

There on the screen was Marinette and Alya just sitting to listen to the radio.

"Fast forward to after I leave."

The video wound forward, black and grey lines of static flickered, splitting the screen in half. He resumed the video as she and Adrien were leaving the room.

They all watched as Nino and Alya held each other, not moving for a few minutes. Marinette wanted to look away – the moment seemed too private – but getting to the bottom of the mystery was too important.

Nino left the room and Alya stayed put, wiping her face with her sleeve then her head snapped up.

"Wait, what was that?" Adrien said, pointing at the screen.

"What?"

"Just there, wind it back a second."

Max did as he was asked and this time Marinette saw it too. Across the room something dark fluttered, landed on Alya and vanished, right before her head came up and the butterfly etched over her eyes.

"Another butterfly?" Marinette asked and Adrien shrugged.

"Thanks, Max," she said. There was nothing more to see here. But then the video was still rolling. Nino came back in the room at the exact moment Alya disappeared. They watched as he ran to where she stood, desperately grasping at nothing.

A moment later, he was gone too.