He shrugged. “I came to ask you a question.” He glanced around the room, his expression bored. “And to show you something. Come. Walk with me.”

She joined him as he left the room, with a mixture of reluctance and relief. She hated her cell, and surely it would be better to see more of the place where she was being kept? The size of it, the exits?

The corridor outside the room was stone, big blocks of limestone slotted together with concrete. The floor was smooth, worn down by footsteps. Yet there was a dusty feel to the place, as if no one had been in it for decades, even centuries.

There were doors set into the walls at random intervals. Jocelyn felt her heart begin to pound. Luke could be behind any of those doors. She wanted to dash at them, jerk them open, but the dagger was still in Sebastian’s hand, and she didn’t doubt for a moment that he knew that better than she did.

The corridor began to curve around, and Sebastian spoke. “What,” he said, “if I did tell you I loved you?”

Jocelyn clasped her hands loosely in front of her. “I suppose,” she said carefully, “that I would say that you could no more love me than I could love you.”

They had reached a set of double doors. They paused in front of them. “Aren’t you supposed to pretend, at least?”

Jocelyn said, “Could you? Part of you is me, you know. The demon’s blood changed you, but did you really think that everything in you otherwise comes from Valentine?”

Without answering, Sebastian shouldered the doors open and stepped inside. After a moment Jocelyn followed—and stopped in her tracks.

The room was huge and semicircular. A marble floor stretched out to a platform built of stone and wood rising against the western wall. In the center of the platform sat two thrones. There was no other word for them—massive ivory chairs overlaid with gold; each had a rounded back and six steps leading down from it. An enormous window, glass reflecting nothing but blackness, hung behind each throne. Something about the room was oddly familiar, but Jocelyn couldn’t have said exactly what.

Sebastian bounded up onto the platform and beckoned her to follow him. Jocelyn moved slowly up the few steps to join her son, who stood in front of the two thrones with a look of gloating triumph on his face. She had seen the same look on his father’s face, when he’d gazed down at the Mortal Cup. “ ‘He will be great,’ ” Sebastian intoned, “ ‘and he will be called the Son of the Highest, and the Devil will give him the throne of his father. And he will reign over Hell forever, and of his kingdom there will be no end.’ ”

“I don’t understand,” Jocelyn said, and her voice came out bleak and dead even to her own ears. “You want to rule this world? Some dead world of demons and destruction? You want to give orders to corpses?”

Sebastian laughed. He had Valentine’s laugh: harsh and musical. “Oh, no,” he said. “You misunderstand me entirely.” He made a quick gesture with his fingers, something she had seen Valentine do when he had taught himself magic, and suddenly the two great windows behind the thrones were no longer blank.

One showed a blasted landscape: withered trees and scorched earth, vile winged creatures circling in front of a broken moon. A barren plateau of rocks spread out before the windows. It was populated by dark figures, each standing a little distance from the next, and Jocelyn realized that they were the Endarkened, keeping watch.

The other window showed Alicante, sleeping peacefully in the moonlight. A curve of moon, a sky full of stars, the shimmer of water in the canals. The view was one Jocelyn had seen before, and she realized with a jolt why the room she was in had seemed familiar.

It was the Council room in the Gard—transformed from an amphitheater to a throne room, but still the same arched roof, the same size, the same view of the City of Glass from what had been two great windows. Only, now one window looked out onto the world she knew, the Idris she had come from. And the other looked out onto the world she was in.

“This fortress of mine has doorways to both worlds,” said Sebastian, his tone smug. “This world is drained dry, yes. A bloodless corpse of a place. Oh, but your world is ripe for ruling. I dream about it during the days as well as the nights. Do I burn the world slowly, with plague and famine, or should the slaughter be quick and painless—all that life, extinguished so quickly, imagine how it would burn!” His eyes were feverish. “Imagine the heights I could rise to, borne aloft on the screams of billions of people, raised up by the smoke of millions of burning hearts!” He turned to her. “Now,” he said. “Tell me I got that from you. Tell me any of that is from you.”

Jocelyn’s head was ringing. “There are two thrones,” she said.

A small crease appeared between his brows. “What?”

“Two thrones,” she said. “And I’m not a fool; I know who you intend to have sit beside you. You need her there; you want her there. Your triumph means nothing if she isn’t there to watch it. And that—that need for someone to love you—that does come from me.”

He stared at her. He was biting his lip so hard, she was sure he would draw blood. “Weakness,” he said, half to himself. “It’s a weakness.”

“It’s human,” she said. “But do you really think Clary could sit next to you here and be happy or willing?”

For a moment she thought she saw something spark in his eyes, but a moment later they were black ice again. “I’d rather have her happy and willing and here, but I’ll take simply here,” he said. “I don’t care that much about willing.”

Something seemed to explode inside Jocelyn’s brain. She lunged forward, reaching for the dagger in his hand; he stepped back, evading her, and spun with a quick, graceful movement, knocking her legs out from under her. She hit the ground, rolled, and crouched. Before she could rise, she found a hand knotted in her jacket, yanking her to her feet.

“Stupid bitch,” Sebastian snarled, inches from her face, the fingers of his left hand digging into the skin below her clavicle. “You think you could hurt me? My true mother’s spell protects me.”

Jocelyn jerked back. “Let me go!”

The leftmost window exploded with light. Sebastian reeled back, surprise blooming across his face as he stared. The blasted landscape of the dead world had suddenly lit up with fire, blazing golden fire, rising in a pillar toward the broken sky. The Dark Shadowhunters were running to and fro over the ground like ants. The stars were coruscating, reflecting the fire back, red and gold and blue and orange. It was as beautiful and terrible as an angel.

Jocelyn felt the hint of a smile touch the corners of her mouth. Her heart was lifting with the first hope she had felt since she had woken up in this world.

“Heavenly fire,” she whispered.

“Indeed.” A smile played around Sebastian’s mouth. Jocelyn looked at him in dismay. She had expected him to be horrified, but instead he looked exalted. “As the Good Book says: ‘This is the law of the burnt offering: It is the burnt offering, because of the burning upon the altar all night unto the morning, and the fire of the altar shall be burning in it,’” he cried, and raised both arms, as if he meant to embrace the fire that burned so high and so bright beyond the window. “Waste your fire on the desert air, my brother!” he cried. “Let it pour into the sands like blood or water, and may you never stop coming—never stop coming until we are face-to-face.”