"You think we should follow it?" Adrien asked, stowing away the helmets.

"I mean," she shrugged, "it's the only lead we have. And what are the chances there would be a real butterfly out in December? I don't think they'd survive the cold."

Adrien nodded. "You're right. Let's follow the butterflies."

They took the opportunity to test out their new gadgets and after a slight hiccough which resulted in them briefly tied together in Marinette's yo-yo string, they quickly got the hang of it. They didn't have far to go but they stuck to the rooftops, not wanting to be seen.

"Where did it go? Do you see it?" Marinette asked.

Adrien had stopped dead, staring blankly at a large mansion where a butterfly was just flitting through an open window.

"Is this the place?" she asked again when he didn't respond.

His face hardened.

"This is it."

He unclipped his staff again and used it to hop the wall. She followed quickly behind.

"There's a security system so stay close," he warned and she glanced about cautiously.

"How do you know that?"

He looked at her over his shoulder, his eyes widening.

"Oh, well, you know. With these big, rich person houses they always have state of the art security, right?"

"Oh. I guess you're right. But how do we get in?"

He nodded up to an open window – different to the one the butterfly went through.

"Up there, we just need to be careful. Hold on to me."

She did as he said and he slowly raised them up until they were level with the second floor window. He pushed it open wider and after a furtive look around, they both stepped inside.

No alarm sounded, in fact there was no sound to be heard at all. The room was dark but Adrien walked confidently forward.

"Where do we go now? There's no butterflies here and this house is huge. The Krampus and the missing elves could be anywhere," Marinette whispered loudly. Adrien turned his head, putting one finger to his lips and beckoned her further into the room.

She looked around, her eyes adjusting to the gloom. This was a bedroom. The large bed on the far side of the room laying testament to that. But it was filled with various entertainments. A climbing wall, skate ramps and a basketball half court barely filled half the space. A mezzanine held dozens, no, hundreds of books and there were gaming systems that made Marinette's mouth water, both classic and modern. There was even a piano!

But for all this, the room felt cold, like a showroom that nobody lived in.

The only place that held any life was the desk.

Next to the three widescreen monitors was a single, framed photograph.

She reached for it.

"Don't-" said Adrien but it was too late.

She stared at the photo silently and Adrien came to stand beside her. Her fingers tightened and she glanced at him from the side of her eye.

"She has your smile," she said, her free hand coming up to touch his cheek, her thumb glancing the corner of his mouth.

He wasn't smiling now.

His eyes tightened.

"We don't have time for this. Let's go and find the Krampus."

He strode out of the room and she followed.

"The house seems pretty empty," she said, their footsteps ringing out and echoing off the walls of the corridor. Adrien walked with purpose, not stopping to open any of the doors. "Where are we going?"

Adrien didn't so much as pause.

"To my father's office. I've never been allowed in there but I think if he isn't here, it might give us some clue as to where the elves are."

"Your fa-"

"He hasn't been the same since we lost mother. And I can only imagine the shame of having his perfect son run away. The attacks started when I got to the Pole, right? This is all my fault."

"Adrien, no!" She grabbed his arm, stopping him in place but he wouldn't look at her. "You can't think that way. Your mother... that can't have been easy. For either of you. You're both hurting, but that doesn't excuse... this. Just because he's in pain doesn't mean he can go around hurting others. For you to come to the North Pole-"

"But I did. I left him and because of that he became the Krampus. But that means it was already a part of who he is. It's in his blood, in my blood. Remember what Fu said? Just like with the Santa's, it's passed on through generations. I am... I will be..." His voice cracked and he squared his shoulders. "But I won't let him do this. I will stop him. We will stop him."

He started forward again, his pace quickening.

In the foyer, the large Christmas tree stood, perfectly uniform and without any lights on, completely devoid of joy. Marinette shivered but Adrien didn't give it a second glance going straight up to a door across the hall. He paused and Marinette put a hand on his arm.

"Adrien?"

This Adrien was one she hadn't met before. Gone were the smiles, the laughter and the wonder that sparkled in his eyes. Instead he was closed off, emotionless. Was this how he coped with his life here in Paris? Was this who he was before he came to Santa's workshop?

It made Marinette want to drag him straight back, Krampus be damned. But they had a job to do.

He opened the door to the office.

Inside it wasn't anything special. A desk with chairs, some sofas, indirect lighting and pot plants. It was stylishly modern but with a large golden painting which was unmistakably Adrien's mother.

"Do you think we might find something on the computer?" Marinette asked, already going to open the desk drawers. Adrien took a seat and unclipped his baton.

"Let's see what 'technological abilities' this thing really has."

He pulled off one end and there was a USB connector. He plugged it into the computer and after a few clicks of the mouse he sighed.

"I can't find anything on here except for work."

Marinette hadn't found anything in the drawers either. Then her eyes came back to the painting. It was the only thing in the room that stood out. Perhaps...

She went over to it, feeling around the edge. There was a catch and it swung open revealing a safe.

"Adrien! Do you think your technological abilities might stretch to safe cracking?"

He came over from the desk. He frowned at the keypad.

"I wonder..." And he typed a few numbers. The light flashed red.

"Do you think this is a good idea? If you don't know the pin-"

"Just one more try," Adrien said, already typing. This time the light flashed green and the safe unlocked, the door opening to reveal some unexpected items. A guide book for Tibet, another picture of Adrien's mother, a peacock brooch and an old looking book. He reached for the book, smoothing a hand over the cover.

"Well if we weren't sure before..."

It was a book on the histories of Santa and the Krampus.

"I'm so sorry, Adrien."

He shook his head, putting it back and closing the safe.

"It's okay. It's not your fault."

"And it's not yours either," she declared again, vehemently.

He looked up at the painting, his mothers smile soft and beautiful, her green eyes a mirror image of his own. Smiling, he ran a hand over the picture.

"I really miss you, Maman."

But as he moved his hand his brows started to draw together. He went back over with his fingers.

"There's something..."

He pressed in and parts of the painting moved but nothing else happened.

"What is it?" Marinette asked, moving closer.

"There's something else with this painting but... maybe... ah!" His other hand found some more indentations. He pushed those in as well and the ground beneath their feet started to move. Slowly the sank into the floor. As they got lower, they found themselves in some kind of glass lift and sprawled out before them was a large cavern with water and plants. It was beautiful. There was a walkway lit up brightly and at the end, a huge tree.

They had found the Krampus' lair.