A snippet was released this week for The Last Hours, coming out in 2018! I’ll give you my theory after you read it:
“Who’s the boy tripping over his own feet?” Cordelia asked as the boy in question, a slender, ink-stained young man with spectacles and tousled brown curls, nearly careened into Lucie and Matthew.
“That’s Christopher Lightwood. My cousin. Alas, Christopher is far more at home with beakers and test tubes than he is with female company. Let’s just hope he doesn’t pitch poor Rosamund Townsend into the refreshment table.”
“Is he in love with her?”
“Lord, no, barely knows her,” said James. “Charles and Daphne are engaged, and Barbara Lightwood has an understanding with George Hayward. Beyond that, I’m not sure I can think of any romances brewing in our set. Though having you and Alastair here might bring us some excitement, Daisy.”
Her heart leaped. “I didn’t realize you remembered that old nickname.”
“What, Daisy?” He was holding her close as they danced: she could feel the heat of him all up and down her front, making her prickle all over. “Of course I remember it. I gave it to you. I hope you don’t intend me to stop using it.”
“Of course not. I like it.” She forced herself not to move her gaze from his. Goodness, his eyes were startling up close. They were the color of golden syrup, almost shocking against the black of his pupils. She had heard the whispers, knew people found his eyes odd and alien, a sign of his difference. She thought they were lovely: the color of fire and gold, the way she imagined the heart of the sun. “Though I don’t think it suits me. Daisy sounds like a pretty little girl in hair ribbons.”
“Well,” he said. “You are at least -“
He broke off. She heard the click as he swallowed: he was looking past her, at someone who had just come into the room. Cordelia followed his glance, and saw a tall woman, thin as a scarecrow and dressed in the black of mourning, with gray-streaked auburn hair done in the styke of decades ago piled on her head. Tessa was hurrying toward her, a concerned look on her face. Will was following, and goodness, what did they both look so worried about?
As Tessa reached her, the woman stepped aside, revealing the girl who had been standing behind her. A girl, dressed all on ivory, with a soft waterfall of white-gold curls gathered back from her face. The girl moved forward gracefully to greet Tessa and Will, and as she did so, James dropped Cordelia’s hands.
They were no longer dancing. Cordelia stood, frozen in confusion, as James turned away from her without a word and strode across the room toward the girl.
Ok so I am guessing the tall, thin woman is Tatiana Blackthorn because she had auburn hair when we meet her in TID, then the girl is her ward, Grace Blackthorn, because James is supposed to fall in love with her and she breaks his heart because she’s a brat. I think they have come to share the news that Jesse Blackthorn (Tatiana’s biological son) is dead. But what I want to know is why is Tatiana wearing the “black of mourning”? The mourning color for Shadowhunters is white, because their gear is black.