CHAPTER 1: DEMONS DIG BLONDES
[S1E1 The Mortal Cup (Part I)]

They were staring at each other, neither of them having blinked in what felt like forever ago. The corners of Margo's mouth turned up as she saw water welling up in Alec's eyes. She smirked, already tasting victory. He was strong though, and his determination helped him last longer in the staring contest. In fact, it helped him last two seconds more than Margo.

She suddenly felt something in her eye and blinked on instinct to rid herself of the irritation. "Hah!" Alec announced, pointing at her. "You blinked!"

"Did not!" The girl denied, feeling Alec do a small victory dance in the form of drumming his fingers on her legs, which rested on his lap. The two were sat on the couch, relaxing before the mission began, when their eyes met and they were suddenly caught in an unspoken contest.

"Admit it. I won." She shook her head. "Margo," he warned, raising an eyebrow at her, his eyes dancing with mischief. "Mango. Admit it."

He liked to call her Mango sometimes. It was a cute nickname.

"No!" she yelped as Alec's hands found their way to her stomach, lightly tickling her as a warning.

"Margo."

"Alec," she mocked, imitating the expression on his face. Margo knew she was treading on thin ice but she lived dangerously around Alec Lightwood. She didn't know why; it sort of just happened.

He brought out her wild side and she couldn't get enough.

Alec couldn't get enough either. He loved when her eyes squinted, the precious giggles came out of her mouth, and she held her stomach because she laughed too hard.

He wanted to emit such actions from her so he continued with his actions and smoothly dug his fingers into her side, forcing a giggle out of her. Oh, how he loved the sound; it was music to his ears.

Through her laughter, she tried to push Alec's hands away. Her legs kicked out, in an attempt to stop Alec, but he went on, dodging her blows until she couldn't take it anymore.

She cried out, yelling, "Okay! You won!" Then his long, slightly calloused hands stopped tickling her. In the process of being tickled, she had slipped down, her knees resting beside Alec as her legs dangled off the couch.

Alec was leaning on his elbow, trapping Margo between his body and the couch. He noticed how close the two were but before he could even get a word out, his younger sister was entering the room, calling out to the girl underneath him.

Upon entering the rather inexplicable scene, Isabelle ushered her parabatai. "M, I need you." She wasn't fazed by the seemingly intimate position she had found her best friend and brother in. "Come on." She held a hand out, waiting as Margo looked between the two Lightwood siblings. Though she loved spending time with Alec, Isabelle was her parabatai, her best friend, and she wasn't ever going to deny her anything.

So Margo nodded her head, turning to part with Alec. The two stood up and Margo took Isabelle's hand before turning back to Alec. "I won," were his final words as he booped Margo's nose and ambled away.

She scrunched her nose, glaring at the older Lightwood as he made his exit. Isabelle noted this and rolled her eyes before leading Margo up to her room. "I need help," she simply stated as Margo plopped down on her bed. Isabelle glanced at the outfit Margo was wearing before mumbling, "And so do you."

She pulled her best friend up, leading her one door down to Margo's room. As Margo took solace in her bed, Isabelle was rummaging through her closet. "Here," she finally said after a few moments of silence. She had laid down a tight, sleeveless red leather dress. "Put it on," she advised after picking out a pair of black pumps to pair with the dress.

"Izzy," Margo groaned. Thought she held that dress very near and dear to her heart, she just wasn't feeling it today. She wanted to go out wearing the jeans and sweater she had on. But Isabelle Lightwood was having none of that. She shook her head at Margo and nudged her towards the dress, leaving the room to attend to her own attire.

Once Margo had put on the dress and the shoes, she made her way over to Isabelle's room, watching from the doorway as she held up two wigs, one blond (or platinum, rather) and one teal. "Go with the platinum," Margo counseled. "For some reason, everyone loves blondes."

"Including demons," Isabelle added playfully. She spun it around in her hand, carefully placing any stray hairs back into place. As Margo softly hummed to herself, Isabelle looked back at her parabatai, wondering. "M, when are you and Alec going to get together?"

Margo's thoughts came to a halt when she heard Isabelle. This was a conversation she'd had many times with Izzy, one she hated having. Before she could speak, her best friend went on. "I mean, you two have practically been dating since you got here, and that was five years ago."

"Izzy, it's not that simple," Margo sighed, picking at the skin around her nails.

Isabelle grunted, moving to stand in front of Margo, who was stood at her doorway. "It is! You two act like a couple already. With literally everything, except the kissing. I wouldn't be surprised if that already happened too."

Margo could feel the blood rushing to her cheeks as she ran a hand through her hair. It was true, she couldn't deny it. Margo and Alec did act like they were together. Ever since they met, they couldn't keep their hands off each other. Whether it was an arm thrown across a shoulder or one on a waist or hands that were interlocked, the two always seemed to find their way back to each other.

Alec was Margo's guy and Margo was Alec's girl. Everyone knew that. That's why none of the other Shadowhunters their age ever tried to romantically involve themselves with one of the pair. They were very public with their relationship; it didn't bother them. They were also very comfortable around each other, which is why they always had a good time.

But their relationship wasn't all it seemed to be. Though alike, Alec and Margo were very different as well. Alec liked to enforce the Clave rules and Margo liked to break them. That was always an issue they had. They didn't fight often but when they did, it got ugly. One time, it even got physical, but they didn't like to talk about that particular moment.

Instead, they chose to ignore it, to sweep it under the rug. One day, though, the rug wouldn't hold and it would break and so would they.

But how could Isabelle even begin to understand why Margo and Alec could be so destructive to each other? They were platonic together but they were also each other's weakness. They could bring each other down with a snap of their fingers and that was detrimental to their friendship.

As Margo tried to form her thoughts into words, the older, raven-haired Lightwood's voice ran through the halls as he rushed the girls. "Isabelle, Margo, let's go."

Margo shrugged as Isabelle urged her to go on and instead walked out the door, hearing her best friend swear before she followed next to her.

"Hey, there, big bro," Isabelle smirked, seeing the way Alec looked between the two, spending a second too long taking in Margo's dress. His eyes shifted over to his sister and the wig she held.

"Really?"

Isabelle shrugged. "What can I say? Demons dig blondes."

He turned to his sister as the three walked up the stairs of the Institute. "Of course they do, but that's white." He pointed to the wig Isabelle held.

"Platinum," she corrected her brother. Alec turned to Margo, hoping for back-up. She shook her head. She had taken his side once against Isabelle on a matter such as this. Isabelle's reaction made sure that it never happened again. Alec groaned, also recalling the incident, and let his sister go on. "And they don't exactly like Shakespeare, okay, Alec?"

He rolled his eyes, mumbling under his breath. "You're plenty distracting on your own."

Isabelle heard, nudging his side and eyeing Margo. "So, be yourself. Is that what you're trying to say?"

Alec understood the gesture. He had been trying to deny his feeling for his best friend and his sister's parabatai. It was useless though; everyone knew of their feelings for each other, even the two people involved. And that was all thanks to Izzy. She had gossiped to Margo about how much Alec liked her and to Alec about the feelings Margo had for him.

"Never mind. Looking good, let's go," he muttered, leading the two girls up to HQ, where Jace stood in front of a large, touch-screen computer.

Margo walked in front of the bickering siblings, greeting the blonde Shadowhunter she had grown to call a brother. "We're ready, Jace."

He glanced back at the trio. "Nice choice, Izzy. Demons dig blondes."

Izzy stuck her tongue out at her older brother. "Told you."

"It's platinum," Alec teased.

Jace turned away from the computer, furrowing his eyebrows at his friends. "All right, guys, for some reason our demon friends are killing mundanes and draining their blood."

He walked a few feet in front of the three, leading them away from the computers. "Why do they want blood?" Alec asked. "Isn't that vampire territory?"

"I don't know, Alec. Lazy vampires, maybe?" Jace guessed.

Izzy perked up. "There must be something special about their blood."

"What could be special about mundane blood?" Alec asked as he conveniently cut his index finger on the edge of a sharp glass table he was walking past. He hissed, shaking his hand violently as she saw blood start to leak out of his finger.

Margo saw this as the perfect teasing opportunity and asked for Alec's hand. Once it was placed in hers, she held his finger and brought it up to her lips, latching onto his finger and swiping her tongue across the wound. Alec quietly gasped and the look of utter shock was clear on his face.

"Yeah, I don't get it. I mean, it doesn't taste anything like Shadowhunter blood," she innocently spoke as she let go of Alec's finger, resuming to her natural state and crossing her arms as she turned to Jace and Isabelle.

Alec, however, still had his mouth agape, his hand up with index finger held out, still damp from Margo sucking on it.

From her peripheral vision, she could see Alec's tense stature and looked to Izzy, winking at her best friend. Her parabatai went on, as if nothing had happened. "You get me a sample and I'll tell you exactly what they're looking for."

Jace pulled open the space in the wall where their seraph blades laid. He handed them out. "We'll have more answers when we figure out exactly who the demons are working for."

"So, you don't think they're acting on their own?" Isabelle asked as she and Jace walked ahead of Margo and Alec.

"No. They're not exactly creative thinkers; they're shapeshifters."

Margo tuned the two out when Alec's free arm slid down Margo's side, leaving tingles as he reached the bottom of her dress, tracing patterns with his fingertips on her bare skin. His hand slipped under the dress, tapping at Margo's upper thigh.

Her breathing quickened, though she'd never let it show. "What do you think you're doing?" she questioned casually as she stopped Alec and stood in front of him. His arm reappeared from under her dress and slipped around her waist.

He smirked. "What? You think you're the only one with the ability to drive the other crazy in this relationship?" He leaned down to her ear, whispering, "Two can play at this game, Go," before tugging at her earlobe with his teeth and quickly letting go. This left the teenage girl in front of him a distraught, hormonal mess.

He pulled back, taking Margo's free hand and smiling at her as if he hadn't just caused one of her ovaries to burst. They caught up to Alec and Isabelle, who stood in front of a large screen.

"Certainly took your time," Isabelle teased the two, eyeing their interlaced hands.

Margo stuck her tongue out at her best friend before focusing on Jace. "This is what our target looks like." On the screen was an elderly Asian man wearing glasses.

"Yeah, for now," Margo added, taking her hand away from Alec's and instead leaning into him, letting him wrap his arm around her waist.

The older Lightwood boy spoke from behind her. "Great. I'll get approval for the mission."

"Come on, Alec. By the time you've sent that message, we'll have killed six demons," Jace stated.

Margo turned around in Alec's arm as they walked towards the exit. "Besides, it's more fun to break the rules than to follow them."

And with that, they were off, into the night, demon-hunting. So, just another casual weekday for the Shadowhunters.