It would be wise for us to continue the lessons, yes, Jem said. But we cannot begin now. The poison consuming those who were attacked is like nothing I have ever seen, nor do the other Brothers know it. We must bend all our will now to finding the cure.

The door opened, and Will stuck his head into the music room. He looked weary, his shirtsleeves rolled to the elbow, his shirt stained with tinctures and salve. Still, he smiled when he saw James and Jem. “Is everything all right?”

“Uncle Jem was worried about me,” said James. “But I am quite well.”

Will came up to his son and pulled him into a quick, rough hug. He said, “I am glad to hear it, Jamie bach. Gideon and Sophie have arrived, and to see them with Barbara—” He kissed the top of James’s head. “It does not bear thinking of.”

I should return to the infirmary, said Jem. There is much still for me to do.

Will nodded, releasing James. “I know Gideon and Sophie would feel better if you were the one tending Barbara. Not to insult Brother Shadrach, who I’m sure is an excellent and well-respected member of the Brotherhood.”

Jem shook his head, which was as close as he got to smiling, and the three of them left the music room. To James’s surprise, Thomas was waiting in the corridor outside, looking hollow-eyed.

Will exchanged a quick glance with James and left his son alone with Thomas. It was good, James thought, to have a father who understood the significance of friendship.

Thomas spoke as soon as the adults were out of earshot. “My parents are here,” he said, in a low voice. “James, I need something to do. Something that might help my sister. I think I might go mad otherwise.”

“Of course—we all must help Barbara,” said James. “Thomas, in the park, Barbara saw the demons before everyone else. She was the one who warned me.”

“She had perfect Sight even before she got her Voyance rune,” Thomas said. “Perhaps because my mother was a Sighted mundane before she became a Shadowhunter. We’ve never been sure—Barbara wasn’t terribly interested in testing her abilities—but she always had unusually keen senses.”

“It is almost as if she could glimpse my shadow realm,” James murmured, remembering what Barbara had said: that she had been able to see ragged black shapes at the ball, that she had felt herself drawn down. An idea had begun to take shape in his mind. He wondered if he should go back and speak of it to Jem, but no—Jem would never let him do it. He would think it was too dangerous. Reckless, even.

But James was feeling reckless, and from the look of it, Thomas was too. “We need to round up Matthew and Christopher,” James said. “I have an idea of what we can do.”