The sparks stung Tessa’s neck like a shower of hot cinders, but she barely noticed; the creature’s arms loosened around her, and she wrenched herself away as it spun and staggered, its arms jerking blindly in front of it. She couldn’t help but be reminded somehow of a sketch she’d seen of an angry gentleman at a garden party waving off bees. Mortmain, noticing a beat too late what was going on, shouted, and the other creatures lurched into motion, surging toward Tessa. She looked around wildly, but could no longer see the tiny angel. It seemed to have vanished.

“Tessa! Get out of the way!” A cold little hand caught at her wrist. It was Jessamine, yanking her backward as Thomas, having released Sophie, dived in front of her. Jessamine thrust Tessa behind her, toward the stairs at the back of the entryway, and moved forward with her parasol whirling. Her face was set with determination. It was Thomas who struck the first blow. Lunging forward with his sword, he sheared through the chest of a creature who was lurching toward him, hands outstretched. The machine man staggered backward, whirring loudly, red sparks spraying from its chest like blood. Jessamine laughed at the sight and laid about her with her parasol. The whirling edge of it sliced through the legs of two of the creatures, sending them toppling forward to flop on the ground like landed fish.

Mortmain looked vexed. “Oh, for goodness’ sake. You—” He snapped his fingers, pointing at an automaton, one that had something that looked like a metal tube welded to its right wrist. “Get rid of her. The Shadowhunter.”

The creature raised its arm jerkily. A bolt of streaky red fire shot from the metal tube. It hit Jessamine square in the chest, knocking her backward. Her parasol skittered from her hand as she struck the ground, her body twitching, her eyes open and glassy.

Nathaniel, who had moved to stand beside Mortmain on the sidelines of the melee, laughed.

A sizzling bolt of hatred went through Tessa, shocking her with its intensity. She wanted to throw herself at Nate and rip her nails down his cheek, kick him until he screamed. It wouldn’t take much, she knew. He’d always been a coward where pain was concerned. She started forward, but the creatures, having dealt with Jessamine, had already swung back around toward her. Thomas, his hair plastered to his face with sweat and a long bloody rent slashed across the front of his shirt, moved to place himself in front of her. He was laying about himself magnificently with the sword, with great, sweeping strokes. It was hard to believe he wasn’t slashing the creatures to ribbons—and yet they proved surprisingly dexterous. Ducking out of his way, they kept coming, their eyes fixed on Tessa. Thomas spun to look at her, his gaze wild. “Miss Gray! Now! Take Sophie!”

Tessa hesitated. She did not want to run. She wanted to stand her ground. But Sophie was huddling, transfixed behind her, her eyes full of terror.

“Sophie!” Thomas cried, and Tessa could hear what was in his voice, and knew she had been right about his feelings for Sophie. “The Sanctuary! Go!”

“No!” Mortmain shouted, turning to the clockwork creature that had attacked Jessamine. As it raised its arm, Tessa caught hold of Sophie’s wrist and began to drag her toward the stairs. A bolt of red fire hit the wall beside them, scorching the stone. Tessa shrieked but didn’t slow, yanking Sophie up the spiral staircase, the smell of smoke and death following them as they ran.

Will dashed through the archway that separated the foyer from the room beyond—and came up short. Jem was already there, staring around him in bewilderment. Though there were no exits from the room other than the one they had just come through, Mrs. Dark was nowhere to be seen.

The room, though, was far from empty. It had most likely been a dining room once, and huge portraits adorned the walls, though they had been ripped and slashed to unrecognizability. A great crystal chandelier hung overhead, fronded with strings of gray cobweb that drifted in the disturbed air like ancient lace curtains. It had probably once hung over a grand table. Now it swung over a bare marble floor that had been painted with a series of necromantic patterns—a five-pointed star inside a circle inside a square. Inside the pentagram stood a repulsive stone statue, the figure of some hideous demon, with twisted limbs and clawed hands. Horns rose from its head.

All around the room were scattered the remains of dark magic—bones and feathers and strips of skin, pools of blood that seemed to bubble like black champagne. There were empty cages lying on their sides, and a low table on which was spread an array of bloody knives and stone bowls filled with unpleasant dark liquids.

In all the gaps between the pentagram’s five points were runes and squiggles that hurt Will’s eyes when he looked at them. They were the opposite of the runes in the Gray Book, which seemed to speak of glory and peace. These were necromantic symbols that spoke of ruin and death.

“Jem,” Will said, “these are not the preparations for a binding spell. This is the work of necromancy.”

“She was trying to bring back her sister, isn’t that what she said?”

“Yes, but she was doing nothing else.” A dreadful dark suspicion had begun to blossom in the back of Will’s mind.

Jem did not reply; his attention seemed to be fixed on something across the room. “There’s a cat,” he said in a low whisper, pointing. “In one of those cages over there.”

Will glanced where his friend pointed. Indeed, a bristling gray cat was huddled in one of the locked animal cages along the wall. “And?”

“It’s still alive.”

“It’s a cat, James. We have bigger things to worry about—”

But Jem was already walking away. He reached the animal’s cage and scooped it up, holding the cage at eye level. The cat looked to be a gray Persian, with a squashed-in face and yellow eyes that regarded Jem malevolently. Suddenly it arched its back and hissed loudly, its eyes fixed on the pentagram. Jem looked up—and stared.

“Will,” he said in a warning tone. “Look.”

The statue in the middle of the pentagram had moved. Instead of crouching, it had straightened until it was standing upright. Its eyes burned with a sulfuric glow. It was only when its triple row of mouths smiled that Will realized it was not stone after all, just a creature of hard gray stonelike skin. A demon.

Will ducked back and flung Israfel reflexively, not really expecting the gesture to do much good. It didn’t. As it sailed near the pentagram, the blade bounced off an invisible wall and clattered to the marble floor. The demon in the pentagram cackled. “You attack me here?” it demanded in a high, thin voice. “You could bring the host of Heaven against me and they could do nothing! No angelic power can breach this circle!”

“Mrs. Dark,” Will said between his teeth.

“So you recognize me now, do you? No one ever claimed you Shadowhunters were clever.” The demon bared its greenish fangs. “This is my true form. An ugly surprise for you, I suppose.”

“I daresay it’s an improvement,” said Will. “You weren’t much to look at before, and at least the horns are dramatic.”

“What are you, then?” Jem demanded, setting the cage, the cat still in it, down on the floor at his feet. “I thought you and your sister were warlocks.”

“My sister was a warlock,” hissed the creature that had been Mrs. Dark. “I am a full-blood demon—Eidolon. A shape-changer. Like your precious Tessa. But unlike her I cannot become what I transform into. I cannot touch the minds of the living or the dead. So the Magister did not want me.” Thin hurt was in the creature’s voice. “He enlisted me to train her. His precious little protégée. My sister as well. We know the ways of the Change. We were able to force it on her. But she was never grateful.”

“That must have hurt you,” Jem said in his most soothing voice. Will opened his mouth, but seeing Jem’s warning look, closed it again. “Seeing Tessa get what you wanted, and not appreciating it.”

“She never understood. The honor that was being done her. The glory that would be hers.” The yellow eyes burned. “When she fled, the Magister’s rage fell on me—I had disappointed him. He swore out a bounty on me.”

That jolted Jem, or seemed to. “You mean de Quincey wanted you dead?”

“How many times must I tell you that de Quincey is not the Magister? The Magister is—” The demon broke off with a growl. “You try to trick me, little Shadowhunter, but your trick will not work.”

Jem shrugged. “You cannot remain in that pentagram forever, Mrs. Dark. Eventually the rest of the Enclave will come. We will starve you out. And then you will be ours, and you know how the Clave deals with those who break the Law.”

Mrs. Dark hissed. “Perhaps he has forsaken me,” she said, “but I still fear the Magister more than I fear you, or your Enclave.”

More than I fear the Enclave. She should have been afraid, Will thought. What Jem had said to her was true. She ought to be afraid, but she wasn’t. In Will’s experience, when someone who ought to be afraid wasn’t, the reason was rarely bravery. Usually it meant that they knew something you didn’t.

“If you will not tell us who the Magister is,” said Will, his voice edged with steel, “perhaps you can answer a simple question instead. Is Axel Mortmain the Magister?”

The demon let out a wail, then clapped its bony hands over its mouth and sank, burning-eyed, to the ground. “The Magister. He will think I told you. I will never earn his forgiveness now—”

“Mortmain?” echoed Jem. “But he is the one who warned us— Ah.” He paused. “I see.” He had gone very white; Will knew his thoughts were chasing down the same winding road Will’s just had. He would probably have gotten there first—Will suspected Jem was in fact cleverer than he was himself—but he lacked Will’s tendency to assume the absolute worst about people and proceed from there. “Mortmain lied to us about the Dark Sisters and the binding spell,” he added, thinking out loud. “In fact, it was Mortmain who put the idea in Charlotte’s head in the first place that de Quincey was the Magister. If it were not for him, we would never have suspected the vampire. But why?”

“De Quincey is a loathsome beast,” wailed Mrs. Dark, still crouched inside her pentagram. She seemed to have decided there was no more point in concealment. “He disobeyed Mortmain at every turn, wishing to be the Magister himself. Such insubordination must be punished.”

Will’s gaze met Jem’s. He could tell they were both thinking the same thing. “Mortmain saw an opportunity to throw suspicion on a rival,” Jem said. “That is why he chose de Quincey.”

“He could have hidden those plans for automatons in de Quincey’s library,” agreed Will. “It is not as if de Quincey ever admitted they were his, or even seemed to recognize them when Charlotte showed them to him. And Mortmain could have told those automatons on the bridge to claim they were working for the vampire. In fact, he could have etched de Quincey’s seal into that clockwork girl’s chest and left her in the Dark House for us to find, as well—all to divert suspicion from himself.”