That room wasn’t one of the hearts, I was sure. But the mirror with its keyhole that I had never been able to open—Shade had never answered any of my questions about it, so it had to be important.

Maybe the Heart of Fire lay on the other side.

It was worth a try. I retraced my steps, thinking of the mirror room. It had always been more mobile than the other rooms; in just a few minutes, I opened a door and saw Astraia sitting on a stone bench in the garden. Her knees were pulled up under her chin, and her forehead was creased in thought.

Movement flickered at the edge of my vision. I spun, expecting a wrathful Ignifex, but instead I saw Shade sliding across the wall behind me, still trapped in his bodiless daylight form. He paused, wavered, and then one of his shadowy hands flowed across the floor to grasp my hand.

My fingers curved around his phantom grip. It had been just the night before last that he released me from the room of dead wives. I remembered crying into his embrace, remembered kissing him and wanting him as surely as I wanted to breathe.

It felt like a hundred years ago. And his quiet presence, once so comforting, made me want to shrink away. I felt like Ignifex’s kisses were written across my face—but surely I should be ashamed instead of kissing the man who was not my husband.

Surely I should be ashamed of kissing the creature who had killed so many.

“Did Ignifex send you?” I asked.

It was hard to tell, but I thought he shook his head, and I supposed that if Ignifex had sent him, it would be with orders to drag me back by the hair, not to ask me nicely.

“I think this is one of the hearts,” I said.

Shade went still, as if the slightest twitch was forbidden, so I knew I was right. Then he let go of me, and I turned to the mirror.

The key slid easily into the lock. When I tried to turn it, at first it stuck; then there was a tiny metallic click, and it turned easily in a half circle. With a high, sharp noise, the mirror cracked down the center.

I jumped back, but nothing else happened. After a moment, I stepped forward and turned the key again. Now there was more resistance; I heard a click-click-click as I turned the key, as if the motion were powering a set of wheels and gears.

Then the mirror shattered into a cascade of glittering dust.

A breath of cold, dry air hit my face. Through the jagged edges of the frame was a dim little room with stone walls; when I stepped over the threshold, I saw that it was the landing for a narrow staircase twisting down into the darkness.

“Can you make light during the daytime?” I asked. But Shade only tugged my hand again. I remembered him singing the funeral hymns beside me and I followed him down the stairs.

Very soon the darkness was absolute. I moved slowly, one hand against the wall, the other gripped by Shade. I could feel the pressure of his touch, but it was bodiless, as if the air itself were gripping my hand. It made me think of how the Children of Typhon had seized me and held me in place for devouring.

I forced myself to focus on the cool, smooth stone beneath my fingertips and the closeness of the air—there was no sense of gaping void in this darkness. There was no icy burn of liquid shadow against my palm. Still my heart beat faster, and my skin prickled as if preparing for terror.

Suddenly Shade let go. I stumbled forward and found I had stepped off the stairs onto the floor. The wall was gone and I groped wildly in the darkness, trying not to panic—

Light dazzled my eyes. I blinked, eyes watering, and saw Shade standing before me, as solid and human as if it were night, a curl of light in his palm. We were in a wide, round room of stone, utterly bare and featureless except for the doorway leading to the stairs, with no light except what glimmered in Shade’s hand.

“How—” My throat was dry and my voice cracked; I swallowed. “How can you have a body during the day?”

“It is always night in this room.” The light glinted in his eyes. He raised the hand with the light higher, and white-gold flames sprang up all around the edge of the room. They made no smoke, but they crackled softly; it was a warm, comforting sound, and warm air flowed over my face. And I felt the thrum of power.

“This is the Heart of Fire,” I said.

Shade nodded. And watched me, the firelight dancing in his eyes.

I squared my shoulders. “Go ahead. Tell me how I’ve done wrong.”

The words jutted between us, harsh and angry. I realized too late they were the sort of thing I would say to Ignifex. They were not anything I should say to the captive who had shown me nothing but kindness.

“He’s taught you anger,” said Shade. “But he hasn’t made you stop trying to save us.”

The anger and cruelty had always been part of me, and Ignifex knew that very well. But at least Shade was still deceived.

“No,” I said. “I’ll never stop. I’ll save you, I promise.”

“Would you die for that?”

“Why do you think I’m here?” I snapped, then drew a breath. “You know I’m prepared to pay any price.”

His fingertips ghosted down the side of my face. “You’ve grown so strong. You’re almost ready.”

“I don’t feel ready,” I muttered.

“You are,” he said. “Trust me.”

You don’t know me, I thought.

He had always comforted me before. But this time, the tension still coiled in my shoulders and stomach. A million words buzzed in my throat: He says he loves me. You kissed me and I wanted it, but I want him too. I believe you’re the prince. It’s my duty to save you and I swear that I will. I think I’m wicked enough to love a demon. Even just thinking them stung like bees, and I swallowed them all.

“You know the Resurgandi’s plan,” I said instead. “Ignifex says it will never work. That we don’t understand the nature of the house at all.”

“Do you trust him?” asked Shade.

I stared into his blue eyes that had once seen the true sun, and in that moment I didn’t want to refuse him anything. I meant to say No, never, of course not. But the words stuck behind my teeth. I remembered Ignifex’s fire driving back the shadows, his body curled trustingly against mine, his voice saying, You lie to me but not to yourself.

Finally I said, “I don’t know what to think. He’s not . . . I don’t trust him. But I don’t think he’s a monster.”

Shade took my hands. “Never doubt this: He is the worst of monsters. He is the author of all our misfortunes, and it would be the greatest blessing if he had never existed.”