The sound of running footsteps in the hall interrupted him. The door flew open again; this time it was Matthew and Lucie, both looking harried. Christopher, who had seized a seraph blade from his belt, lowered it in relief. “Thank Raziel,” he said. “I thought it was a demon attacking.”

Matthew gave Christopher a dark look. “Put that away,” he said. “I don’t fancy being stabbed; I am far too young and beautiful to die.”

“I see you have been waylaid on your way to find socks, James,” said Lucie. “Bridget came and told us Christopher was here. What’s going on? Has anything happened?”

“Quite a lot of things, actually,” said Christopher. “We can discuss it all at the Devil Tavern. Thomas is waiting there, and I do not want to leave him alone.”

* * *

The Devil Tavern was a half-timbered building on Fleet Street with vast glittering windowpanes that seemed to divide light, leaving the interior of the pub darkly shaded. There were very few people inside, only a few men hunched over tankards of ale, but a grizzled werewolf barkeep and his wide-eyed barmaid watched Lucie, Cordelia, James, Christopher, and Matthew cross the room and ascend the steps, their gazes curious.

Cordelia was unsurprised to see that the walls of the Merry Thieves’ rooms were crowded with fascinating-looking books. There was an antique-looking dartboard in which several throwing daggers were embedded, its embossed red-and-black surface showing the marks of many more. There was a corner with sheets of metal fixed to the walls and a sturdy steel-topped worktable, upon which sat a set of shiny brass scales and a somewhat battered-looking wooden beer crate filled with glass test tubes, retorts, and other chemistry paraphernalia. A mobile laboratory for Christopher, Cordelia assumed.

A low horsehair sofa was placed directly across from a fireplace whose mantel boasted a bust of Apollo, below which was carved a verse about wine. Thomas sat upon the sofa, a book in his hand. His broad shoulders were hunched, his eyes shadowed with exhaustion. Still, his face lit up when he saw his friends.

“Tom,” said James. He went and sank down next to his friend on the worn sofa, placing a hand on his shoulder. He glanced up and saw the others still hesitant. He gestured for them to join him and Thomas. It was always James, Cordelia thought as they drew up chairs. Always James keeping the group together, noticing when they needed each other.

Thomas set down the book he’d been holding; Cordelia was startled to see it was a book of Sufi poetry, the verses of Hafiz and Ibn al-Farid, written out in Persian and Arabic. “Cordelia,” he said. He sounded weary, as if his voice had been slowed by grief. “Lucie. I’m glad to see you.”

“Welcome to our sanctum, ladies,” said Matthew, unscrewing the cap of his flask. “Christopher salvaged quite a bit of this furniture for us. Like King Arthur and his knights, we prefer to sit at a round table that we all might be equal.”

“Also,” Christopher added, taking a book down from the shelves and handing it to James, “it was the only table my mother was willing to spare.”

“I couldn’t go to Idris,” Thomas said rather suddenly, as if someone had demanded of him why he was still in London. “I wish to see Eugenia, but I need to stay here. I need to help Kit find the cure for this demon disease or poison or whatever this is. What happened to my sister cannot happen to someone else.”

“Sometimes grief and worry must take the form of action,” said Cordelia. “Sometimes it is unbearable to sit and wait.”

Thomas shot her a grateful look. “Exactly that,” he said. “So—Christopher told you all about the shards?”

“Yes,” Christopher interjected, “and James realized the shards are from a Pyxis.”

“A Pyxis?” Thomas echoed. “But they were destroyed after the Clockwork War. They’re unsafe—remember what happened at school.”

“Most Pyxides were destroyed after the Clockwork War,” said James. “In Gast’s flat, though, I found a drawing. It looked rather like a sketch of an ordinary box—he wasn’t a very good artist—”

“Ah, the drawing with the wobbly runes around it?” Matthew said.

“They weren’t runes,” James said. “They were alchemical symbols—the kind you’d carve onto a Pyxis box.”

“Oh!” said Lucie. “The markings on the shards. They were alchemical symbols too. Of course.”

“That wasn’t all,” said James. “On the paper Gast had scrawled a word in Old Persian. Cordelia was able to translate it.”

He looked at her expectantly.

“It was a demon’s name,” Cordelia said. “Merthykhuwar.” She frowned. Such demons had featured in old stories from her childhood; she had always thought of them as near-mythical, like dragons. “In modern Persian it would be Mardykhor. But Shadowhunters—Shadowhunters call it a Mandikhor. They are said to be viciously poisonous.”

“You think Gast summoned up a Mandikhor demon?” Matthew asked. “But aren’t they meant to be extinct? And what’ve they got to do with Pyxis boxes?”

James flipped open the book Christopher had handed him and slid a pair of small gilt reading glasses onto his nose. Something in Cordelia’s chest tightened, as if she had snagged a small piece of her heart, like a piece of cloth on a thorn. She looked away from the sight of James and his adorable spectacles. She had to find someone else to feel this way about. Or someone to feel a different way about. Anything, so she could stop feeling like this.

She tried not to think about what he had said in the training room. I no longer have an understanding with Grace. But why? What could have happened between them, and happened so quickly?

“ ‘The Mandikhor is both here and there, both one and many,’ ” James quoted. “See, one of the nastiest things about the Mandikhor is that it can split itself into many pieces, each of which is both its own separate demon and a part of the original creature. That’s why they’re best captured in Pyxis boxes. The Mandikhor is difficult to kill—partly because it can produce an endless stream of smaller demons; you’d find yourself not even being able to get near it. But with a Pyxis, if you use the box to capture the Mandikhor, the smaller demons will disappear.” He looked up from the book. “I started to guess it was a Pyxis when Christopher told me about the shards. Cordelia’s translation confirmed it. I knew Gast must have summoned up one of the few demons he would need a Pyxis to capture. In this case, a Mandikhor.”

“It doesn’t look anything like those creatures that attacked us at the park,” said Christopher, peering over James’s shoulder. The book was illustrated, but Cordelia didn’t need to see it: she knew what a Mandikhor looked like. Scorpion tail, lion body, triple row of jaws dripping poison.

“I am fairly sure those were the Khora,” offered Cordelia. “The smaller demons that split from the Mandikhor. They do not resemble it. And that must be why Gast referred to the demon in the singular—he did raise one demon. It split into smaller demons later.”

“So someone hired Gast to raise a Mandikhor and trap it in a Pyxis,” said Lucie. “But when he returned to his flat with the demon caged in the box, they ambushed and killed him—and set the creature free.”

“Gast is not the mind behind this,” James agreed. “He was a tool, useful only for building a Pyxis and summoning the demon. Someone else is directing its movements and attacks.”

“Not just summoning the demon,” said Lucie. “Remember what Ragnor said—Gast summoned it in such a way, using dimensional magic, that it is protected from sunlight.”

They all exchanged glances. Cordelia knew what the others were thinking—who could have hired Gast? Was there no motive save to spread bloodshed, contagion, and death?

Thomas ran a hand through his thick hair. “If the demon were trapped and killed, what of those who are poisoned? Would they get better?”

James shook his head. “The sick will not be healed. We still need an antidote for that. But the demons will be gone, and that is quite a start.” He set the book down. “The Enclave has been searching for these demons with no success—how would they have guessed they were seeking the offspring of an extinct creature? But now that we know it is a Mandikhor…”

“In the stories of Merthykhuwar demons, they make their homes in between spaces,” Cordelia said slowly. “For instance, the border between two countries, or the middle of a bridge. Somewhere that is neither here nor there.”

James drew off his spectacles; he was biting his lip thoughtfully. “When I went into the shadow realm, from the ballroom,” he said, “I saw—among others things—Tower Bridge. A strange red light poured from it. I think—”

Matthew sat up straight. “We know Gast raised the demon from a bridge,” he said. “A place between, as Cordelia said. Perhaps it still resides there.”

“So if we were to go to Tower Bridge, with a Pyxis, it’s possible that we could recapture the Mandikhor?” said Lucie. “And then the Khora would disappear—just as if it had died?”

“Yes, but we’d have to get a Pyxis first,” said Christopher practically. “That would be difficult.”

“But perhaps not impossible,” said Matthew. He was tapping his fingers restlessly against the arm of his chair, his hair and necktie disheveled. “If most were destroyed after the Clockwork War…”

“A few remain,” said James. “Unfortunately, they’re in Idris.”

“I was afraid you were going to say that,” muttered Matthew, reaching for his flask again. “I think it will be noticed by the Clave if we disappear from London and turn up in Idris, rooting around the Gard like treasure hunters.”

James gave him an exasperated look. “The only Pyxides in the Clave’s possession are in Idris. There are a few others. We just need to find one. There’s a certain shop in Limehouse—”