Title: Not In Your Lifetime (An AU The Mortal Instruments/The Infernal Devices crossover fic based on notesfromcecilyherondale and notesfromsebastianmorgenstern on Tumblr)

Characters Involved: Cecily Herondale (The Infernal Devices) & Sebastian/Jonathan Morgenstern (The Mortal Instruments)

Rated (chapter): K+ (Cue the sigh from disappointed readers!)

Chapter A/N: I haven't written fanfiction in a while so forgive my rustiness. I hope to get better with practice (so keep sending in those questions for character muse!) Thanks to Obsidian (on Tumblr) for the invaluable input! :D

CHAPTER 1

Her hand went from the roots of her hair until the very ends with a steady rhythm. Cecily Herondale found all the solace she needed through the dark strands that slipped from her fingers, her own dark blue eyes staring back at her from the mirror. The clock on her vanity read five minutes past eight in the evening. Her lips quirked to the right and she shook her head, chuckling.

"Late. What else would I expect from a demon child?" she thought as her fingers worked through her hair still.

Another minute passed and another, her rhythm getting slower at every heartbeat. What had gotten into her head, agreeing to this meeting? The scandal of it all – the impossibility; William would have never approved. He would have insisted into her luring of this little demon child into his death, not a date. Still, Cecily was no fool as she had a few seraph blades tucked in the confines of her bodice, skirts, and sleeves – just in case.

A knock sounded from her door and Sophie opened it by a margin, only to allow her head entrance. Cecily turned her head, fingers at the very ends of her hair. "Visitor for you, Miss Herondale."

"Who might that be?" she asked, though she already knew. "I'm not expecting any visitors."

A deep cough came from behind the maid servant and Cecily couldn't help but smile. "A young Mr. Morgenstern, miss."

"Don't let him in and tell him to wait. That will be all, Sophie."

Sophie nodded and closed the door behind her. Cecily turned back to the mirror on her vanity and looked herself once over. Her dark hair cascaded downward in waves, just surpassing her breasts. She bit her lips and pinched her cheeks for colour, as Mother always said. She brushed herself off, her borrowed dress was in the colour of violets. She put on her long, dark gloves over her hands and gave her hair one last brush over. She did all this as slow and loud as possible – slow enough to keep him waiting, loud enough for him to hear her slowness.

A parasol rested on the foot of her bed and she took it for good measure. It was a modified one that Henry gave to her and a girl could never walk out the streets of London without enough weapons. She opened the door halfway, looking at her impossible visitor for the first time. She eyed him once ever and not briefly at that.

The saying "devilishly handsome" did not come out of spite. Clad in dark fitting dress clothes, contrasting the silver blond of his hair with streaks of black here and there. He was a head or two taller and he was smirking at her in way that told her he had compromised many a woman with that same look. She could only purse her lips bemusedly and raise her eyebrows at his demeanour. He looked so sure of himself and he radiated compromise. She opened the door and stepped out of her room, staring into his eyes that were as black as coal.

"So you can get on consecrated ground," was the first thing she said.

He grinned crookedly and ducked his head a little. "We've been through this, love. I'm not a demon."

"Was it difficult to get to the Institute, then? Charlotte hindered you? Or perhaps dear William did?"

"No. Just the maid girl," he shrugged.

"Then I don't see any reason for your tardiness."

He chuckled and licked his upper lip. "My apologies, love. Shall we?" he asked, offering her his arm politely.

She looked at his arm and back at his face. Cecily only turned her head and walked past him. Their walk from her room to the door was a silent one as she was always one step ahead of him. She only stopped at the door before he opened it. A carriage was waiting beyond the Institute gates. He offered her his hand and that time, she took it and allowed herself in. They were seated on opposite sides of each other, the carriage riding along the cobblestone streets of London.

Cecily leaned her head against the window, looking through the glass at the passersby who were still out at that time of night. She could barely see her companion; the shadows secluding him, as the only thing she could make out were the outlines of his face and his silver blond hair that seemed to glow in the darkness. Not that she was looking but she could feel his eyes on her.

He cleared his throat but she stayed silent; the carriage lurched on, undisturbed by the silence of its passengers.

"You look lovely," he said.

"I know." Her face was unreadable, her eyes still on the night time streets of London.

Silence ensued. She was making things difficult and she knew it. She liked the discomfort that her behaviour often caused. She was a wall – one would have to climb in order to get to the other side. Besides, what would she say? Would she ask of the future, of what future the Shadowhunters of his century faced? Their correspondence should have been impossible but for some way, somehow – there they were. But she was not interested in the future; her eyes were on her present and how she was going to live through it.

"Are you going to be difficult all night?" The humour had gone from his tone. No longer playful, no longer patient.

"Are you going to let me?" she looked to him now, searching for his eyes in the darkness. "Nothing worth having comes easy, darling. I've made myself quite clear: I will not go to you."

The carriage slowed to a stop and when she looked out, she found that they were outside a small theatre. Her eyebrows quirked up and she remained very still; he stepped out first, waiting to assist her down.

"What are we doing here?"

"There's a play here tonight. I thought you might enjoy it," his voice was low, soft, and careful. She smiled as she stepped out of the carriage, straightening herself up.

His hand was on her elbow politely, ushering her inside. The audience was fairly small and it was nothing too lavish. It was simple and the audience probably the family members of the actors who were bound by duty to watch it as many times as it would run. The play itself was awful and she loved it. The props were falling apart, the curtains opened and closed at inappropriate times, two or five actors forgot their lines, and there was a rather loud disagreement conspiring backstage – loud enough for everyone in the audience to hear it. She was laughing for most of the play, her fingers twirling the ends of her hair.

He was barely watching the play – he was watching her. He laughed when she did, smiling whenever she would stifle a giggle. As cold as she might try to be, she was still a girl. He found himself pulled into her strange allure. She was cynical and knowingly seductive. And yet she laughed like a little girl, smiled like no one was watching her. In all her fierce charm, she was – in a word – adorable. Everything in him told him to attack, to pursue and destroy. Something inside him yelled at him to see blood, to hear that strong, soft voice scream for mercy while he ripped her apart, piece by piece. He kept it in, fighting the urges he was hearing in his head. He wanted to hear her scream but the scream he wanted was in a completely different light.

By the end of the play, a girl was running out of the stage in tears with a grown woman walking behind her, a stern expression on her face. Cecily pressed her lips together and laughed to herself.

"I didn't realize that this was what you meant when you said you liked to play."

He smiled shyly, as if he was capable of modesty. The audience dispersed from the theatres soon enough. The two of them seemed to be the only ones in good spirits as they left the theatre. The carriage was not waiting for them outside the theatre as she had anticipated. Instead, he led her a few blocks down, to bridge near the Thames.

The streets were dimly lit as clouds started to gather, warning of more rain. Whatever era of time he was in, it was almost always raining in London. Cecily already had her parasol resting on her shoulder, shielding her from the rain that was yet to come. There was a hubbub of noise from nearby restaurants and homes, people still up and about at that time of the evening.

"What it's like?" asked Cecily. "In New York."

"Dreadful. Filled with too many people I would rather have dead."

Silence sparked once more as they walked by the Thames, the only sound that could heard was the soft clip clap of the heel on her shoes. She was looking into the distance, the full moon that was decorated by stars and dark gray clouds. The light of the moon reflected off of the water from the river, illuminating her face. He was right to call her beautiful because she was. Her blue eyes were hypnotic – like the water of the Thames itself.

"I prefer London. I prefer this era."

"The weather's dreadful enough to drive you mad," she remarked, remembering the days in Wales wherein there was a little more colour to the sky than blacks and greys.

"Perhaps I'll show you around New York, then. Take you to my time, then maybe you'll see what I mean."

She looked to him, piercing him with those same blue eyes that made him want to repent and confess all his sins but never would if it meant never seeing those eyes again. "Maybe if you're a good little demon child. We'll see."

The walk back to the Institute was a quiet one. Drizzle had dawned upon them, then the uncompromising rain. By the time they got back to the familiar Church, her skirts and gloves were soaked with water while he was almost completely drenched. From the gates, she led the way again. From the complicated yet familiar hallways, she found her way back to the room that she was hers. She stopped at the door and turned to face him.

"You never did take me to dinner," she said, cocking her eyebrows, a smirk on her lips.

"Let me take you to New York next time. My era." He had that look again; the same devilishly handsome stance that he had when she first saw him at her door. She chuckled and shook her head. Did he really think her as one of the exploits that he had of so little dignity? Still, he intrigued her and he was a damn more exciting sight that watching William brood over his own life. She pressed her lips and nodded twice, choosing to indulge the demon child once more.

He smiled at her and bowed before her, as a proper London gentleman should. He raised one of her hands to his lips and kissed it. Her gloved hands was still on his lips when he whispered, "I look forward to seeing you again."

The smirk on Cecily's lips grew to a crooked grin as she quickly took the hand he was holding and used it to pull him down to her. She was stronger than she looked (and the superhuman strength rune helped too). Her other hand rested on his chest in order to stop him from completely crashing into her, the hook of her parasol hanging on her arm. Both his palms were at her door, resting just beside her waist, for balance.

Their foreheads were touching, their noses millimetres apart from each other. She reached up a little and rubbed her nose against his just a bit, just to tease. She parted her lips and sighed, her breath was warm and smelled of peppermint tea. She reached up just a bit more, as her lowered the hand that was on his chest to the door handle behind her, and kissed him on the bridge of his nose, to his disappointment. She moved quickly as she twisted herself away, opened her door from behind and went behind it.

But before she closed it, she looked over him once more, grinning.

"Oh I know you do."