The sound of sirens echoed in Emma’s ears, the howl of the fire brigade, hurtling toward the church. Julian drew away from her, only far enough to clasp her hand. They fled from the church just as the first of the fire engines arrived.

* * *

Mark didn’t really know how they’d all gotten into the library. He vaguely remembered going to check on Tavvy—who was building an elaborate tower of blocks with Rafe and Max—and then to knock on Dru’s door; she was in her room, and disinclined to come out, which seemed like a good situation. There was no reason to frighten her before it was necessary.

Still, Mark would have liked to see her. With Julian and Helen gone, and now Ty and Livvy somewhere in London, in danger, he felt like a house whose foundations had been ripped out from under it. He was desperately grateful that Dru and Tavvy were both safe, and also that at the moment, they didn’t need him. He didn’t know how Julian had done it all those years: how you were supposed to be strong for other people when you didn’t know how to be strong for yourself. He knew it was faintly ridiculous for him, an adult, to want the company of his thirteen-year-old sister to fortify his resolve, but there it was. And he was ashamed of it.

He was conscious of Cristina, speaking in rapid-fire Spanish to Magnus. Of Kieran, leaning on one of the tables, his head hanging down: His hair was a purple-black color, like the darkest part of water. Alec returning from the hallway with a pile of clothes in his hands. “These are Ty’s, Livvy’s, and Kit’s,” he said, handing them to Magnus. “I got them from their rooms.”

Magnus looked over at Mark. “Still nothing on the phone?”

Mark tried to breathe deeply. He’d called Emma and Julian as well as sending texts, but there had been no reply. Cristina had said she’d heard from Emma while she was in the library, and they both seemed to be fine. Mark knew that Emma and Julian were smart and careful, and that there was no better warrior than Emma. Worry pinched at his heart just the same.

But he had to focus on Livvy and Ty and Kit. Kit had next to no training, and Livvy and Ty were so young. He knew he’d been the same age when he was taken by the Hunt, but they were children to him nonetheless.

“Nothing from Emma and Jules,” he said. “I’ve tried Ty a dozen, two dozen times already. No answer.” He swallowed back the dread. There were a million reasons Ty might not pick up his phone that didn’t have to do with the Riders.

The Riders of Mannan. Even though he knew he was in the library of the London Institute, watching as Magnus Bane began passing his hands over the clothes, beginning the tracking spell, part of him was in Faerie, hearing the tales of the Riders, the murderous assassins of the Unseelie Court. They slept beneath a hill until they were wakened, usually in times of war. He’d heard them called the King’s Hounds, for once they had a whiff of their prey, they could follow them across miles of sea, earth, and sky in order to take their lives.

The King must want the Black Volume very badly, to have brought his Riders into it. In old days, they had hunted giants and monsters. Now they were hunting the Blackthorns. Mark felt cold all over.

Mark could hear Magnus speaking in a low voice, also explaining the Seven: who they were and what they did. Alec had given Cristina a gray shirt that was probably Ty’s; she was holding it, a Tracking rune on the back of her hand, but she was shaking her head even as she clutched it tighter. “It isn’t working,” she said. “Maybe if Mark tries—give him something of Livvy’s—”

A black flounced dress was shoved into Mark’s hands. He couldn’t picture his sister wearing something like it, but he didn’t imagine that was the point. He held it tightly, sketching a clumsy Tracking rune onto the back of his right hand, trying to remember the way Shadowhunters did this—the way you blanked your mind, reached out into the nothingness, trying to find the spark of the person you sought at the other end of your own reaching imagination.

But there was nothing there. The dress felt like a dead thing to his touch. There was no Livvy in it. There was no Livvy anywhere.

He opened his eyes on a gasp. “I don’t think this is going to work.”

Magnus looked confused. “But—”

“Those are not their garments,” said Kieran, lifting his head. “Do you not recall? Clothes were lent to them when they arrived here. I heard them complaining of it.”

Mark wouldn’t have thought Kieran had been paying enough attention to what the Blackthorns had been saying to take note of such details. Apparently he had.

But that was the way of Hunters, wasn’t it? Seem as if you are paying no attention, but absorb every detail, Gwyn had often said. A Hunter’s life can depend on what he knows.

“Is there really nothing of theirs?” Magnus demanded, a slight edge of panic in his voice. “The clothes they were wearing when they got here—”

“Bridget threw them away,” said Cristina.

“Their steles—”

“They would have with them,” said Mark. “Other weapons would be borrowed.” His heart was hammering. “Isn’t there anything you can do?”

“What about Portaling to the Los Angeles Institute?” said Alec. “Grabbing some of their things from there—”

Magnus had begun to pace. “It’s barred from Portaling right now. Security concerns. I could look for a new spell, we could send someone to dismantle the block on the California Institute, but any of those things takes time—”

“There is no time,” said Kieran. He straightened up. “Let me go after the children,” he said. “I pledge my life I will do everything I can to find them.”

“No,” Mark said, rather savagely, and saw the stricken look that passed over Kieran’s face. There was no time to explain or clarify, though. “Diana—”

“Is in Idris and cannot help,” said Kieran. Mark had slipped his hand into his pocket. His fingers closed on something small, smooth, and cold.

“It might be time to summon the Silent Brothers,” said Magnus. “Whatever the consequences.”

Cristina winced. Mark knew she was thinking of Emma and Jules, of the Clave meeting in Idris, of the ruination and danger the Blackthorns faced. A ruination that would have taken place on Mark’s watch. Something that Julian would never have allowed to happen. Disasters did not happen on Jules’s watch—not ones he couldn’t fix.

But Mark couldn’t think of that. His whole mind, his heart, was filled with the image of his brother and sister in danger. And they were more than his brother and sister at that moment: He understood what Julian felt when he looked at them. These were his children, his responsibility, and he would die to save them.

Mark drew his hand out of his pocket. The gold acorn glittered in the air as he threw it. It struck the opposite wall and broke open.

Cristina whirled. “Mark, what are you—?”

There was no visible change in the library, but a scent filled the room, and for a moment it was as if they stood in a glade in Faerie—Mark could smell fresh air, dirt and leaves, earth and flowers, copper-tinged water.

Kieran had tensed all over, eyes full of a mixture of hope and fear.

“Alec,” Magnus said, reaching out a hand, and his voice was less a warning than a sort of stripped-down urgency—the uncanniness of Faerie had come into the room, and Magnus was moving to protect what he loved. Alec didn’t move, though, only watched with steady blue eyes as a shadow rose against the far wall. A shadow with nothing to cast it.