I'm unsure of how likely it would be that the London Institute would be aware of a Greater Demon that appears in the MI series (being so many years later and on a different continent) but bear with me. The italicized quote belongs of course, as mentioned, to Charles Dickens but can also be found in chapter 10 of Clockwork Angel, 'Pale Kings And Princes'.
"Will, not even you would be foolish enough to assume that you can just run off to face a Greater Demon that you've never heard of before -"
"On the contrary Charlotte, that is exactly what I intend to do. Where's the fun in life if we know what's coming, eh? There isn't any!"
"Really Will, it's just plain -"
"I don't think -"
Jem's calm, quiet voice broke across the discussion, barely echoing around the dining room where they were gathered. "I think you should at least consider finding out a little more about this demon before you send me chasing after it, Will."
Will fixed his parabatai with a measured glance, well aware of Jem's intentions. If there was anyone Will would listen to, it would be James, a fact Charlotte had long come to terms with. Will kept himself separate, alone – so he could avoid situations exactly like this; there was no possible collateral damage if he didn't care for anyone else. Jem's illness meant that he needed to be extra careful and Will would be damned if he was the reason Jem lost the battle. Jem was well aware of the fact Will would listen to him and often had to use it to his advantage; Will's recklessness, his complete disregard for his safety, his downright suicidal nature was one day going to lead him into a situation he could not escape from. Jem knew Will felt as if he didn't have much to live for and knew that it was his job to make sure Will didn't push his humanity too far. His greatest worry was always, always the same: what would become of his hunting partner when the illness claimed him?
Will exhaled slowly, eyes focused on Jem "fine."
He pushed away from the table and stalked towards the door before turning back and surveying the people sat around the table; Jessamine, looking bored, Henry, Charlotte, Jem and –
He closed his mind on the thought before it could take up residency in his mind. She was not here.
"What exactly am I looking for," he drawled "on this wild goose chase?"
"Agramon," Henry said, tinkering with something on the table "his name is Agramon and he'll be quite a challenge to destroy, I believe."
Will crossed his arms and laced his voice with sarcasm. "Why Henry, it does appear you are privy to some information that I, the person who has to go and kill the bloody thing, do not know. Care to share?"
"Will!" Charlotte chided him "don't speak to Henry like that. We have a library. Put it to use."
Muttering to himself, Will turned sharply on his heel and let the door slam behind him. His patience was short at the best of times; Henry seemed to be able to burn the candle quicker than it took him to light the damn thing.
He took the stairs two at a time and made it to his room quickly. He grabbed the book he had finished the night before and tucked it under his arm as he headed back down towards the library. As he passed Tessa's door he noticed that there was no light peeking underneath it and shook the thought from his head. It wasn't until he reached for the handle of the library door that he remembered how much she loved the room he was about to enter and it had become her favourite haunt ever since he had spoken so coldly to her that night on the roof. Her escape, he supposed, grimly. Yes, they were alike that way; they ran into the pages of the books they devoured as a way of dealing with their lives. Shaking his head, he pushed the door open quietly and stuck it through the small gap he'd created. Sure enough, there she was: sat on a high backed chair in the middle of the library with her legs thrown up over the arm rest, a book perched on top of them. He couldn't see her face as it was hidden behind the back of the chair, but he could see her bare feet and ankles, exposed where the folds of her dress had no hope of reaching. All the lamps were out and the light from the candle on the table next to her was waning; he could only imagine how her eyes must be hurting, if she was even still awake. It was getting late, the darkness pressing silently against the window.
He cursed quietly under his breath and told himself quite firmly that it was a grave misfortune that he had happened across her in this manner... but yet... he could not seem to make himself believe it. They had not spoken properly since that evening, merely the bare necessities: "good morning" and "could you pass the salt?"
The door closed behind him with an echoing bang as he slipped through. He winced and quickly averted his eyes as he saw her peer out from around the chair. Not asleep, then. No, very much awake. He saw her pull her feet back quickly and felt a little remorse. He had not wished to disturb her and he had liked how relaxed she had been. He had liked walking in on her reading, causally slumped back in a chair with no regard for manners or what was considered appropriate for behaviour for a lady, and found he could quite easily imagine doing that every night for a very long time.
He swallowed noisily and pressed on. The damage was done and she was suitably disturbed. They would both just have to face the awkwardness like the adults they had not quite yet become.
Will kept his back to her as he silently moved towards the A section and began to thumb through the books. There was barely enough light coming from Tessa's candle for him to see what he was looking at and he was forced to turn and face her, ducking quickly towards a lamp and swiping it from a table near her. She was staring resolutely at the page she was reading, her legs tucked underneath her, showing no other sign that she had seen him.
Chewing his lip, he went back to the section he had been inspecting and lifted the gas lamp, lighting it quickly. Squinting, he passed over every book and could not find the one he wanted.
Frustrated with both his inability to find what he needed and the thick tension in the room, he started again, exhaling sharply. He heard a book close behind him and stiffened before looking back at the books.
"Do you... do you need some help?"
Her New York accent seemed so loud through the silence. He turned slowly and looked across at her, perched on the chair, her naked feet pointed towards the floor as she held them in a stance that told him she was preparing to stand. He gulped and turned back to the shelf quickly. How easy it was for her to turn him from the harsh, cruel person he had become and into a mess that stuttered when she so much as spoke!
"Oh, I was just looking for a book on a Greater Demon, not something I'd imagine you know anything about."
There, he'd done it again; hurt her, pushed her away with his sharp tongue. He felt the instant taste of regret fill his mouth like bile and choked on it soundlessly. He stepped back and hit something solid.
He spun and found himself face to face with an ashen faced Tessa. "Why don't you try me, Mr Herondale? After all, it is you who gave me a book with information about them in it, wasn't it?"
He looked down at her, the anger written across her face leaping out at him, and nodded. She placed her hands on her hips and glanced behind him at the section he had been examining.
"Firstly, you're looking in the wrong place," she said, so sure of herself that he did not doubt her. She turned and headed towards the G section of the library and he trailed after her. "Greater Demon is under G," her voice was all business, void of emotion. She had never been crisp with him like this before, he thought; she must have learnt it from him. The thought made him grimace.
"Thank you," he murmured, the gas lamp swinging in his hand beside him.
"Yes, well," she said, looking flustered "what's its name?"
"Agramon. Henry says he's hard to kill."
"All Greater Demon's are," she said distractedly, reaching up towards a book that was just out of her reach. Surprised at her knowledge, it took Will a moment to realise what she was doing. He moved forward and reached a hand up. "Let me."
His hand accidently brushed hers as they both stretched for it and she drew hers away quickly, stepping to the side as he pulled it down. Cheeks burning, she pulled it from his grasp and moved towards the candle, collapsing back into her chair. Will stood rooted to the spot before moving quickly towards the chair next to her, shaking his hand off as he went. He cleared his throat and sat next to her, watching her flick through the book and land on a page only a few from the very first.
"Here," she said, pushing a dark curl back from her face as she leant over the desk, sliding the book towards him. "Agramon."
His eyes danced over her face as she looked down at the page, the candle lengthening her eyes lashes and causing dramatic shadows across it. His hand suddenly, without his consent, shot out and gripped her wrist gently, but firmly.
"Tess..." he murmured, not taking his eyes from her face. She had gone very pale again and he watched her bite her bottom lip. She suddenly wished she had lit all the lamps rather than the one candle that was bathing them both its warm light. She looked up at him and yanked her hand free of his grip.
"If that's all, Mr Herondale" she said brusquely, turning away from him and picking her book up, opening back to the page she had been reading. He glanced at the title and cracked a smile.
"'And yet I have had the weakness, and have still the weakness, to wish you to know with what a sudden mastery you have kindled me, heap of ashes that I am, into fire.'"
Tessa peered over the copy of Dicken's A Tale of Two Cities, eyebrows raised. "You do bemuse me, Will."
He took it as a good sign that she was calling him by his Christian name again. "How so?"
"You act as if you don't care at all, and then you quote such a line. You want to be careful."
"Of what?" He said, head tilted to the side.
She ducked back behind her book but he could see the blush across her cheeks. "You may start giving people the wrong impression, you say things like that."
They fell into silence as Will considered what she had said. After a while he said "I don't say things like that often."
Tessa couldn't think of anything to say that wouldn't start an argument between them again, so she kept her face hidden behind the barrier the book created between them.
"Only to you."
She felt her heart fly into her throat and her cheeks began to burn. She peeked over the top of the book at him with wary eyes. "That's only because we talk about literature."
"True," he said, relaxing back against the chair "it wouldn't do much for my reputation if everyone knew I love books. It doesn't bode well to love much, you see."
"Why, that's an awful thing to think!" Tessa said, dropping the book into her lap. "There are always better reasons to love then there are to hate."
"Love gets you hurt," he said with a shrug "Jem will die. That will hurt. You won't speak to me. That hurts."
Tessa stumbled over her words as she tried to reply. "I – Mr Herondale -"
"Don't call me that, Tess," he said, sitting forward in his chair suddenly "call me Will, it's what you know me as -"
"I wonder if anyone very well 'knows' you, Will," she said closing her book with a snap. "All I wanted to do was just read my book. Excuse me." She moved to stand and he spoke quickly, before she could leave.
"I am sorry, Tess," he said quietly. She bit her lip, pushing down on the thrill that ran through her when he said her nickname, the one he had given her. She was still hurt from what he had said – not just the way he had made her sound, like just another one of those girls he professed to have been with – but also the way he had told her, quite coldly, that she would never have children of her own. She hadn't exactly wanted them soon, but it had always been part of a future plan. She supposed she was angry at him for the truth as much as she was angry at him for being the messenger.
"I lost everyone I loved, Will. My own brother turned away from me, for money and power. You and Jem and Charlotte, Henry and Jessamine, Sophie – you're all I have in the entire world, whether you would permit it or not." She shot him a hard look and stood, clutching her book. "I know that love hurts, but I am also of the opinion that love is all we have to live for."
Will stood quickly and suddenly his face was only centimetres away from hers. He stared down at her, eyes blazing and cupped her cheeks quite suddenly, pulling her towards him as he bent and kissed her, his lips moving gently with hers. She was surprised by the way he was holding her, treating her, as if she was something precious and important and shocked herself even further kissing him back, pressing her lips firmly against his. The book fell from her hand and landed on the floor next to them with a thump. The kiss became more passionate as one of his arms wrapped itself around her waist and pulled her closer to his body. He kissed her with a force she remembered all too well from their first kiss, up in the attic. The thought made her lips freeze and she pulled away from his. He was breathing heavily, his eyes still closed, one hand on her wrist again.
"You seem to have a curious interest in my wrist," she said quietly, head turned from his.
"My curious interest is in you, Miss Gray," he said, his nose nuzzling her cheek. He kissed her neck softly and pulled back to look at her. "What is it?"
"I'm just waiting for the moment," she said softly, staring at the floor "you break my heart again."
They stood in silence for a moment before Will let out a strangled sob and pulled her back towards him and wrapped his arms around her, holding her body close to his. She was shocked by his reaction to her words and stiffened in his arms before relaxing and tentatively hugging him back, burying her face in the crook of his neck. Maybe, she thought, Will was not as awful as he wished the world would think he was.
They stood holding each other in silence until the candle burned out, the Greater Demon long forgotten.