It's a little late but I decided to write something a little Christmassy that involves Will and Tessa in the 21st century. There's also a couple of surprise characters in there just cause anyone who knows me knows I adore them all and, well, it's Christmas! So yes, AU, but equally as satisfying as if it was in Victorian England.

They are still Shadowhunters, and when Will refers to the thing that stopped him, he is indeed talking about what stopped in CP, just, it didn't happen then but now. Hopefully it's pretty easy to all understand. It's really just some light fluff to celebrate the holidays.

I dedicate this to my amazing friends on tumblr who understand what it's like to ship a pairing until you cry in your soup and never want to leave your bed again.

He pulled up outside her house and pulled on the handbrake, switching off his car. He stared up at her window for a moment, seeing her bedroom light on and didn't move. This is stupid, he thought to himself, stupid. Suddenly his strong arms, corded with muscle from his Shadowhunting duties, whipped out and slammed against the steering wheel. He rested his head against the leather. He shouldn't be here. It was wrong. But that didn't stop him from open the door and stepping out into the night, closing the door behind quietly him, locking it with a click. He turned and took in a deep breath, the freezing December air cutting into his chest.

I shouldn't be here.

But it didn't feel wrong.

Will couldn't fight how right it felt, echoing through his chest like a song from his childhood, one his mother would murmur to him as she brushed his dark hair from his face on nights he couldn't sleep. He stared at the little gate that led up to the door and watched as a petite redhead walked past the window of the kitchen, yawning.

If Jace can do it, I can. Will thought, steeling his nerve. His cousin had always been smooth with the ladies, but when he'd met Clary, everything had changed. Will had remembered laughing at him for it at the time, but now he knew how Jace had felt.

Hunkering down further in his dark coat, Will pushed the gate aside and strode to the door. Christmas decorations lit the street but the girls' house was empty of them. The pair were due to fly out to New York City tomorrow for Christmas in the Institute over there.

He knocked, but no one answered. He knocked harder and squinted through the frosted glass but he couldn't see anything. He turned and went back down the pathway and stood underneath Tessa's window.

"Tess," he called. There was still no answer.

Feeling frustrated, Will pulled out his phone and flipped through his phonebook. He didn't want to call her; he wanted to do this in person. He didn't have Clary's number, so he quickly dialled his cousin.

"Jace," he said, watching his breath steam through the cold night. "I need your help."

"Interesting words, cousin," the blonde drawled from the other end of the phone. "What with?"

"I'm trying to tell Tessa I love her," he replied, fighting the urge to punch Jace when he saw him. "I need you to let me in her house."

"Didn't you knock?"

"Yes," Will said exasperatedly, "no one answered."

"Maybe no one is in. Or maybe they just didn't want to answer to you, I could understand why..."

"Oh no," Will said sweetly, "I definitely saw Clary. Wearing a little pair of shorts that just framed her perfectly -"

"Alright," Jace cut in with a low growl, "I'll come over."

"Thought you would. See you soon."

Eventually, Jace arrived. He took one look at his cousin and sighed.

"Get it together, dude," he said, striding down the path and slipping his key in the door, "you look like a little lovesick puppy."

"Much like you did before you got together with Clary, then," Will said, crossing his arms. Jace shrugged.

"Beautiful women have always been the downfall of Herondale men," he said, pushing open the door for his cousin. "Now, go get her tiger."

Will pushed past Jace and headed straight for the stairs. He heard Jace enter the kitchen and a surprised squeal emit from Clary. He listened to their mumbling as he reached the top of the stairs and with a deep breath, turned to face Tessa's door.

I want that, he thought as he lifted a hand and knocked. I want this.

The door opened and Tessa stood before him in nothing but a pair of shorts and a white cami, her dark hair pulled into a loose bun and her feet bare.

I want you.

Swallowing hard, Will cleared his throat.

"Uh, hi Tessa," he said as calmly as he could.

"What are you doing here, Will?" she asked, looking perplexed. He shuffled from one foot to the other and shrugged.

"I just wanted to see you."

"See – see me?" she replied, looking confused.

It's no wonder she's confused, Will thought to himself angrily, when have I ever been anything but a jackass to her? She probably thinks I hate her.

But things have changed now.

"There was something – something that stopped me," he said earnestly, stepping towards her, his strong body dwarfing her as he moved closer. Her toes curled as his tough boots rested against her foot. "I couldn't tell you the truth, Tess," he said, gripping the door frame as he looked at her, eyes wide in earnest, "because I would rather have suffered my whole life than let anything happen to you.

He watched her throat as she swallowed and her tongue darted out and wet her lips. She looked away from his stormy eyes quickly and cleared her throat.

"Do you want to take your coat off?" she said, "I'll get you a drink."

She pushed past him and made her way downstairs.

"Tess?" Will called after her, perplexed. He turned and followed her back down the stairs and into the kitchen, where Jace and Clary were sat. Clary was on Jace's lap on the comfy chair they had in there, her head resting on his shoulder as they talked quietly. Their fingers were interlocked and Jace was smiling in a way Will could only describe as looking complete.

Tessa was in the corner bustling around getting a glass.

"What are you guys doing?" Clary asked, lifting her head from her boyfriend's neck and watching them with knowing eyes. Will shrugged and looked back at the brunette.

"How did you even get in, Will?" Tessa asked, glancing at Jace, who smiled angelically.

"I was just coming over and I found a stray on the doorstep," the blonde shrugged. "He gave me puppy dog eyes, it was impossible to say no."

Tessa looked back down at the glass as she turned on the cold tap. "Will," she said quietly, "take your coat and stuff off."

Will took them off and hung them over a chair around the table. Tessa approached him and gave him the glass. He wrapped his fingers around hers purposely as he took it from her and she flushed bright scarlet. Pulling away quickly, she tucked some stray hair behind her ear and turned to her housemate.

"Are we still ordering pizza, Clare?" Tessa said. Clary nodded and cuddled closer to Jace.

"Don't you just love snuggling?" Jace said mischievously. Clary looked at him as if to say what the hell? before she noticed the look on his face and quickly agreed with him.

"Oh yeah," she said, pretending to shiver. "It can get so cold in this house and Tessa, you're wearing exactly the same as me! You must be freezing! Maybe you need someone to warm you up?"

"I'm fine," Tessa said pointedly, glaring at her best friend.

Will looked from the couple on the chair to Tessa and back again.

"Will -"

"So I'm going back upstairs," Tessa said loudly, speaking over the top of Jace, "you guys have fun. Be safe. You know."

Jace laughed as Tessa turned and disappeared back towards the stairs. Will hurried after her and, thanking the Angel as he glanced upwards, grabbed her wrist, turning her to face him.

"Will, what -"

He walked forward and captured his lips with hers. He felt her gasp and nearly fall backwards but one arm came around her waist tightly and held her up. One of her hands curled into his tight, dark blue long sleeved shirt and the other tentatively touched his cheek. He growled low in his chest and pulled her tighter against him, showing her just how okay it was for her to touch him. She became more confident after that, slipping her fingers through his hair and letting him guide her backwards until one of his knees was resting on the staircase and she was sitting next to it, letting him push her back against the stairs behind her. One arm stayed wrapped around her but the other cupped her face gently, pulling it up so he could kiss her better, harder. Then it slipped down her throat and along her shoulder, down her arm before he entangled their fingers together.

She broke away first, turning her head to the side, chest heaving. Will's lips dropped to her neck and her back arched against the stairs, but she pushed him back breathlessly.

"Will," she gasped, a hand on her chest. "Will. What the hell was that?"

He dipped his head back towards her and nuzzled her neck. "Mistletoe," he whispered, his warm breath hitting her naked shoulder and making her shiver. She looked up and sure enough, a sprig hung above them.

"Will, I..."

He kissed her shoulder chastely and pulled back, standing up and looked down at her, his eyes burning.

"I know you're going to New York tomorrow, Tessa," he said, and he grabbed her hand and pulled her flush against him. "I just wanted to make sure you got your present from me first."

Tessa's mouth opened and closed several times before she let her hand fall to his toned stomach and she leant against him. "Will."

"Don't forget me, when you're out there, Tess," he whispered, pulling her against him with a hand on her lower back. Then he pulled away and strode back into the kitchen, leaving Tessa alone in the hallway still trying to catch her breath.