Old Faithful licked its lips. Walden heard Nikki whisper, “How is it like—a person?” She held the dead boy’s gaze.

2003: the death of Charlie Green. A typical story of schoolboy hubris, Philomela had said, as if Charlie had been just any boy, an interchangeable boy, the Platonic ideal of adolescent foolishness—a concept, not a person. There was a photograph of him gathering dust in the school archives, a memorial plaque outside Scrubs, and a tree planted near the site of the old cricket pavilion that after twenty years no longer looked new.

Walden—Saffy—had been seventeen years old. The Marshals had dragged her away screaming, before they collapsed the incursion.

Charlie must have shielded himself through the detonation. He’d still been alive. He’d still been alive, the last time she saw him, before he was left behind for Old Faithful, alone.

The body—the corpse—that Old Faithful was wearing had not aged a day, of course. He probably even had his guitar calluses still. Walden remembered finding him fantastically fit. Impossible to see it now. Nothing had changed: he was still tall, blond, with the chin-length shaggy haircut that every teenage boy with pretensions to counterculture had worn in the noughties, but these were not the things that struck her now. Instead she could only see how his skinny height had not yet filled out in the shoulders and torso, how the last traces of childhood chubbiness lingered around his soft cheeks, how badly he’d shaved the erratic blond fluff on his chin and upper lip. You were so young, Walden thought. She could have wept. Oh, Charlie, you were so, so young.

“Did you miss me, Saffy?” Old Faithful said sweetly.

Walden had spent a considerable portion of the twenty years since Charlie was consumed by this monster becoming one of the world’s foremost experts on higher demons. She was not fooled. “No need for games, thank you. Just your answer. Now,” she said. “Do we have a deal or not?”

“But if I let them go,” the demon said, “what’s to stop you leaving too? I felt you punch that portal earlier.” It grinned at her—Charlie’s earnest, sideways grin, with Charlie’s wonky canines. It reached into the pocket of its jeans and pulled out a familiar penknife. “Give me a guarantee.”

Walden fumbled the catch, and had to stoop and pick up the penknife without taking her eyes off Old Faithful. She knew what it was asking for. Blood pacts with demons were an ancient practice—a largely obsolete practice, because the risk so reliably outweighed the reward. If you gave a demon a piece of your physical self, you were giving it an opening that would last as long as you lived. The profound stupidity of what Walden was about to do weighed on her. But she could not see another way to force it to let both Nikki and Mathias go.