Alec fired an arrow into the demons chest before it could finish its leap to Izzy. The girl smiled, finishing off another demon who had attacked her from the front.

"Thanks big brother but I had that."

Alec fired another arrow, this one behind him, right through the eye of a demon whom he hadn't even bothered to turn around for. He smiled back at his little sister.

"I know you did."

Jace kicked the last demon hard enough to send it toppling backwards, impaling itself on Izzy's ready blade.

Jace and Izzy started advancing towards the rouge warlock that had been causing so much trouble, while Alec hung back, bow and arrow aimed to the ready in case he tried anything.

Izzy was confident as always, strutting towards the warlock with a smug look, and while Jace was smiling he had his blade raised to the ready. The warlock was trapped, drained of magic with no place to run. A desperate look was in his eye, one that made Alec tense because someone who was that desperate would do anything, and warlocks always had tricks up their sleeves.

The mission was to bring the warlock in but when Alec saw the potion bottle being thrown he fired, the arrow hitting its mark and sending the Warlock down. Alec watched in horror, mouth open in a yell and feet already moving forward because the potion bottle had been thrown at Izzy. The glass shattered in front of her and the shadow hunter was instantly enveloped in light and smoke.

Alec shouted his sisters name, about to reach into the smoke for her when Jace pulled him back. Alec only managed to wrestle his arm out of his brothers grip after the smoke cleared, revealing Izzy on the floor looking dazed.

The elder Lightwood pulled away from Jace to kneel beside his little sister, placing a hand on her back to steady her swaying.

"Izzy? You okay?"

The girl nodded though she still looked shaken.

"Yeah, I think so. Whatever he threw at me was probably jut meant as a distraction."

Jace sighed in relief from behind the two brunets.

"Or it was just a dud. He was almost completely drained of magic."

Jace looked towards the body of the warlock, Alec's arrow standing up from its chest.

"Looks like we won't be getting that information out of him like we wanted."

Alec nodded, face emotionless as always. "We should still take him back to the institute, and Izzy you need to be checked over in case the potion did something to you that we can't see yet."

"I'm fine Alec. Let's just get this done and go home."

…..

Alec had stayed with Izzy till she had been cleared from the infirmary. She had declared she was fine, that he worried too much. He had frowned and watched her walk to her room, to bed. She looked okay and she wasn't swaying like she had been. She'd be fine. The shadow hunter had gone to bed, exhausted from the days mission, only to be plagued by dreams of Izzy disappearing into the smoke of the potion. She'd disappear with a scream and had been gone when the smoke cleared. Alec woke with a start, muscles tense, and shook the images from his mind. Izzy was fine he had seen her himself.

The Lightwood threw his blankets off and was just climbing out of bed when there came a tapping at the door.

"Come in."

There was a pause before the tapping started again. Sighing, the shadow hunter walked to the door and opened it only to be greeted by….nothing.

Alec frowned, eyebrows furrowing over his bright eyes before he heard a squeak from the floor. A little girl was standing at his feet, wrapped in a blanket and smiling up at him, small enough that her head had to be titled right back to see him from where she stood. Her bare feet tapping the floor as she started bouncing in excitement.

"Alec!"

Her long dark hair flew everywhere and she smiled so big he could see all of her teeth. She looked to be only a few years old but he knew immediately who it was.

"Izzy?"

The girl lifted a hand and made grabby hands at Alec, her other hand gripped to the blanket around her. Alec frowned and bent down to pick her up like she obviously wanted. He held her to his chest and looked down at her as she threw her arms around his neck and squeezed.

"Big brother's so biiiiiig."

Alec couldn't stop the smile that overtook his face. As bad as this situation was it was hard to deny how adorable she was. His little sister was suddenly a child again and at the moment all she seemed to want to do was cuddle with her big brother. Mother wouldn't be happy. The Clave would certainly have something to say about this.

Alec hugged the squirming girl back and carried her with him as he made his way to his phone. Holding Izzy with one hand as she played with his hair, the boy dialed the one person he knew that could fix this.

"Hey Magnus I….. no this isn't about that. I know we haven't had that dinner yet but I need your help. Could you just come to the institute please? Discreetly if you can, just meet me in my room. Magnus…. No not for that…. I can't explain it right now but it's not for that."

Alec blushed furiously at what Magnus was suggesting but finally got a cheeky "I'll be there soon" from the warlock. Alec shook his head and looked at Izzy as she placed her little hands on his cheeks.

"I hope you didn't hear any of that."

She only giggled and kissed his nose which made him smile wider. Alec sat on his bed and held Izzy on his lap as he started tickling her, her squirming and giggled squeals making the usually resigned shadow hunter laugh himself as his little sister exploded into laughter.

He loved his sister, he had never hid that, it was just always hard to bond with her over anything other than killing demons. She got mad at him because he never talked to her about his personal life, he didn't talk about his personal life with anyone it wasn't just her, but now that she was little again they could spend time together just playing. It was nice.

Alec stopped tickling her and waited till she caught her breath again before talking.

"Izzy do you know what happened? Is this because of the potion?"

The girl looked up at him and laughed while slapping her tiny palms on his cheeks. Alec smiled again and decided she probably had a mind that matched the age of her body.

Sparks came from the wall next to Alec's bed and a purple wall of swirls and light appeared, flickering and warping as Magnus stepped through it. The warlock was smiling and looked appreciatively at Alec in his sweat pants and t-shirt before focusing on little Izzy.

"Oh, I didn't realize you had such young children in the institute. Who's this?"

Alec tugged his little sisters hands away from his face and raised his eyebrows at Magnus.

"This is Izzy."

The warlock titled his head, confused and a little disappointed.

"This is why you called me. Had a bit of a mix-up with some runes did you?"

Alec shook his head, watching Magnus as he sat on the bed beside them.

"We were after a rouge warlock last night and Izzy got hit with some potion. Nothing happened and she seemed fine but this morning she came to my door like this. I was hoping you could help."

Magnus smiled, crossing his legs and gesturing with his painted fingers and jeweled hands.

"To be honest I am a little disappointed you didn't call me to do something else. We are in your bedroom after all and such a lovely bed. But yes I will do everything I can do to help return your sister to normal."

Alec blushed again and looked away from Magnus to stop from smiling.

Magnus smiled, pleased at Alec's reaction before leaning down a little to look at the little girl in Alecs lap.

"Let's have a look at you my dear Isabelle."

Izzy sat on Alec's knees as the warlock swirled his glowing hands around her, Alec had to hold her little fidgety hands with his so that she didn't try and grab the blue flames of magic flowing from Magnus.

The warlock sighed and gave his hands to Izzy to play with as he produced light from them to entertain her.

"The potion had taken her back to her child self. She is free from all her runes and will have the mind of her child self. I cannot reverse this particular spell but it will wear off within a few days. She'll return to herself, most likely in her sleep, and be fine. Take it as an opportunity to spend some time with her."

Alec held his sisters tummy as she slapped at Magnus' hands.

"Thank you Magnus. I'll get you you're payment as soon as –"

Magnus interrupted quickly. "Nonsense, anything for you Alexander. Just tell me when you're free for dinner and we'll call it even."

Alec smiled and licked his lips, no matter how hard he tried Magnus always had a way of making him smile.

"Sure, as soon as Izzy is back to her normal self we'll…. Have dinner."

Magnus stood, smiling wide enough for the corners of his eyes to crinkle underneath his glitter and eye-shadow.

"Magnificent!"

The warlock bowed with a flourish, keeping eye contact with the smirking shadow hunter.

"Until then."

The purple wall appeared again, enveloping Magnus before disappearing, leaving Alec alone with Izzy.

"This should be fun to explain."