“Someone’s here,” Will muttered back. Without another word he and Jem turned so that their backs were to each other. Jem faced the open front doorway; Will, the vast curving stairs.

Something appeared at the head of the stairs. At first Will saw only an alternating pattern of black and white, a shadow that moved. As it drifted downward, the singing sound grew louder, and the hairs on Will’s neck prickled more. Sweat dampened the hair at his temples and ran down the small of his back, despite the chill air.

She was halfway down the stairs before he recognized her—Mrs. Dark, her long, bony body clad in a sort of nun’s habit, a shapeless dark robe that fell from her neck to her feet. A lightless lantern swung from one clawed hand. She was alone—though not quite, Will realized as she paused on the landing, for the thing she was clutching in her hand was not a lantern after all. It was her sister’s severed head.

“By the Angel,” Will whispered. “Jem, look.”

Jem looked, and swore too. Mrs. Black’s head dangled from a plait of gray hair, which Mrs. Dark clutched as if it were a priceless artifact. The head’s eyes were open, and perfectly white, like boiled eggs. Its mouth hung open too, a line of dried black blood threading from one corner of the lips.

Mrs. Dark stopped her song and giggled, like a schoolgirl. “Naughty, naughty,” she said. “Breaking into my house like this. Bad little Shadowhunters.”

“I thought,” Jem said under his breath, “that the other sister was alive.”

“Maybe this one brought her sister back to life and then chopped her head off again?” Will muttered. “Seems a lot of work for no real gain, but then …”

“Murdering Nephilim,” Mrs. Dark snarled, fixing her gaze on Will. “Not content with killing my sister once, are you? You must return and prevent me even from giving her a second life. Do you know—have you any idea—what it’s like to be entirely alone?”

“More than you can ever imagine,” Will said tightly, and saw Jem glance at him sideways, puzzled. Stupid, Will thought. I shouldn’t say such things.

Mrs. Dark swayed on her feet. “You are mortal. You are alone for a moment of time, a single breath of the universe. I am alone forever.” She clutched the head to her tightly. “What difference does it make to you? Surely there are darker crimes in London that more urgently require the attention of the Shadowhunters than my poor attempts to bring back my sister.”

Will’s gaze met Jem’s. The other boy shrugged. Clearly he was as confused as Will was. “It’s true that necromancy is against the Law,” Jem said, “but so is binding demon energies. And that does require our attention, quite urgently.”

Mrs. Dark stared at them. “Binding demon energies?”

“There is no point in pretending. We know your plans exactly,” said Will. “We know of the automatons, the binding spell, your service to the Magister—whom the rest of our Enclave is, right now, tracking to his hiding place. By tonight’s end he will be utterly erased. There is no one for you to call on, nowhere for you to hide.”

At that, Mrs. Dark paled markedly. “The Magister?” she whispered. “You have found the Magister? But how …”

“That’s right,” Will said. “De Quincey escaped us once, but not this time. We know where he is, and—”

But his words were drowned out—by laughter. Mrs. Dark was bent over the staircase railing, howling with mirth. Will and Jem stared in confusion as she straightened up. Blackish tears of hilarity streaked her face. “De Quincey, the Magister!” she cried. “That poncing, preening vampire! Oh, what a joke! You fools, you stupid little fools!”

18

THIRTY PIECES OF SILVER

Blot out his name, then, record one lost soul more,

One task more declin’d, one more foot-path untrod,

One more devil’s-triumph and sorrow for angels,

One wrong more to man, one more insult to God!

—Robert Browning, “The Lost Leader”

Tessa staggered back from the door. Behind her, Sophie was frozen, kneeling over Agatha, her hands pressed to the older woman’s chest. Blood soaked through the pitiful cloth bandage under her fingers; Agatha had gone a horrible putty color and was making a noise like a teakettle boiling. When she saw the clockwork automatons, her eyes widened and she tried to push Sophie away with her bloody hands, but Sophie, still screaming, clung tenaciously to the older woman, refusing to move.

“Sophie!” There was a clatter of footsteps on the stairs, and Thomas burst into the entryway, his face very white. In his hand he gripped the massive sword Tessa had seen him holding earlier. With him was Jessamine, parasol in hand. Behind her was Nathaniel, looking absolutely terrified. “What on earth—?”

Thomas broke off, staring from Sophie, Tessa, and Agatha to the door and back again. The automatons had come to a halt. They stood in a line just inside the doorway, as still as puppets whose strings were no longer being pulled. Their blank faces stared straight ahead.

“Agatha!” Sophie’s voice rose to a wail. The older woman was still, her eyes wide open but unfocused. Her hands hung limply at her sides.

Though it made her skin prickle to turn her back on the machines, Tessa bent and put her hand on Sophie’s shoulder. The other girl shook her off; she was making little whimpering noises, like a kicked dog. Tessa darted a glance behind her toward the automatons. They were still as motionless as chess pieces, but how long could that last? “Sophie, please!”

Nate was breathing in pants, his eyes fixed on the door, his face as white as chalk. He looked as if he wanted nothing more than to turn and run. Jessamine glanced at him once, a look of surprise and disdain, before turning to Thomas. “Get her on her feet,” she said. “She’ll listen to you.”

After a single startled glance at Jessamine, Thomas bent down and, gently but firmly, pried Sophie’s hands from Agatha, raising her to her feet. She clung to him. Her hands and arms were as red as if she had come from a slaughterhouse, and her apron was nearly ripped in half and was printed with bloodied handprints. “Miss Lovelace,” he said in a low voice, keeping Sophie close against him with the hand not holding the sword. “Take Sophie and Miss Gray to the Sanctuary—”

“No,” said a drawling voice from behind Tessa, “I don’t think so. Or rather, certainly, take the servant girl and go where you like with her. But Miss Gray will be remaining here. As will her brother.”

The voice was familiar—shockingly so. Very slowly Tessa turned.

Standing among the frozen machines as if he had simply appeared there by magic was a man. Just as ordinary-looking as Tessa had thought he was before, though his hat was gone now, and his graying head was bare under the witchlight.

Mortmain.

He was smiling. Not as he had been smiling earlier, with affable cheerfulness. His smile now was almost sickening in its glee. “Nathaniel Gray,” he said. “Excellently done. I admit that my faith in you was tested—tested sorely—but you have recovered admirably from your past missteps. I’m proud of you.”

Tessa whirled to look at her brother, but Nate seemed to have forgotten she was there—that anyone else was there. He was staring past her at Mortmain, the oddest expression—a mix of fear and worship—stamped on his face. He moved forward, pushing past Tessa; she reached to hold him back, but he shook off her reaching hand with a flick of annoyance. At last he was standing directly in front of Mortmain.

With a cry he went to his knees and clasped his hands in front of him, almost as if he were praying.

“It was only ever my desire,” he said, “to serve you, Magister.”

* * *

Mrs. Dark was still laughing.

“But what is it?” Jem said in bewilderment, raising his voice to be heard over her peals of laughter. “What do you mean?”

Despite her ragged appearance Mrs. Dark managed an air of triumph. “De Quincey isn’t the Magister,” she sneered. “He’s just a stupid bloodsucker, no better than the others. That you were so easily fooled proves you have no idea who the Magister is—or what you’re facing. You’re dead, little Shadowhunters. Little walking dead men.”

That was too much for Will’s temper. With a snarl he lunged toward the steps, his seraph blade outstretched. Jem called for him to stop, but it was too late. Mrs. Dark, her lips drawn back from her teeth like a hissing cobra’s, swung her arm forward and flung her sister’s severed head toward Will. With a yell of disgust he ducked aside, and she took the opportunity to charge down the steps, past Will, and through the arched doorway at the west side of the foyer, into the shadows beyond.

Mrs. Black’s head, meanwhile, bumped down several stairs and came to rest gently against the toe of Will’s boot. He looked down, and winced. One of her eyelids had drooped closed, and her tongue hung, gray and leathery, out of her mouth, for all the world as if she were leering at him.

“I may be sick,” he announced.

“There’s no time for you to be sick,” said Jem. “Come on—”

And he dashed through the archway after Mrs. Dark. Nudging the warlock’s severed head out of the way with the toe of his boot, Will followed after his friend at a run.

* * *

“Magister?” Tessa repeated blankly. But that’s impossible. De Quincey is the Magister. Those creatures on the bridge, they said they served him. Nate said … She stared at her brother. “Nate?”

Speaking aloud was a mistake. Mortmain’s gaze fell on Tessa, and he grinned. “Seize the shape-changer,” he said to the clockwork creatures. “Don’t let her go.”

“Nate!” Tessa cried, but her brother did not so much as turn to look at her, as the creatures, brought back to sudden life, lurched forward, whirring and clicking, moving toward Tessa. One of them seized her, its metal arms like a vise as they encircled her chest, crushing the breath out of her.

Mortmain grinned at Tessa. “Don’t be too hard on your brother, Miss Gray. He really is cleverer than I gave him credit for. It was his idea that I lure young Carstairs and Herondale out of the place with a far-fetched tale, that I might enter unmolested.”

“What’s going on?” Jessamine’s voice trembled as she looked from Nate, to Tessa, to Mortmain, and back again. “I don’t understand. Who is this, Nate? Why are you kneeling to him?”

“He is the Magister,” said Nate. “If you were wise, you would kneel too.”

Jessamine looked incredulous. “This is de Quincey?”

Nate’s eyes flashed. “De Quincey is a peon, a serf. He answers to the Magister. Few even know the Magister’s true identity; I am one of the chosen. The favored.”

Jessamine made a rude noise. “Chosen to kneel on the ground, are you?”

Nate’s eyes flashed, and he scrambled to his feet. He shouted something at Jessamine, but Tessa could not hear it. The metal mannequin had tightened its grip on her to the point where she could barely breathe, and dark spots were beginning to float in front of her eyes. She was dimly aware of Mortmain shouting at the creature to loosen its grip on her, but it did not obey. She clawed at its metal arms with weakening fingers, barely aware of something fluttering at her throat, a fluttering that felt as if a bird or a butterfly were trapped beneath the collar of her dress. The chain around her neck was vibrating and twitching. She managed to look down, her vision blurred, and saw to her amazement that the little metal angel had emerged from beneath the collar of her dress; it soared upward, lifting the chain over her head. Its eyes seemed to glow as it flew upward. For the first time its metallic wings were spread, and Tessa saw that each wing was edged with something shimmering and razor-sharp. As she watched in amazement, the angel dived like a hornet, slashing with the edges of its wings at the head of the creature holding her—slicing through copper and metal, sending up a shower of red sparks.