“Bee,” I say. “In fifteen minutes, light the fire.”

She nods imperceptibly, and I move out of the kitchen and to the rotunda. The drum tower thuds six times. According to Helene, the Warden will head to the interrogation cells in a quarter-hour. No time, Laia. Move.

I bolt up the rotunda’s narrow stone staircase. It ends in a wood-beamed hallway lined with dozens of doors. Masks’ quarters. Even as I get to work, the silver-faced monsters exit their quarters and head down the stairs. Every time one passes, my stomach clenches and I look down at myself, making sure my invisibility is still intact.

“Do you smell something?” A short, bearded Mask stumps down the hall with a leaner companion, only to stop a few feet from me. He takes a deep sniff of the air. The other Mask shrugs, grunts, and moves on. But the bearded Mask continues to look about, sniffing along the walls like a hound that’s caught a scent. He stops short at one of the beams I’ve anointed with oil, his eyes dropping to the pool gleaming at its base.

“What in the hells …” As he kneels down, I slip behind him, to the end of the hallway. He spins at the sound of my footsteps, his ears keen. I feel my invisibility falter at the rasp of his scim leaving its scabbard. I grab a torch off the wall. The Mask gapes at it. Too late, I realize that my invisibility extends to the wood and pitch, but not the flame itself.

He swings his sword, and startled, I back away. My invisibility drops entirely, a strange rippling that starts at my forehead and cascades down to my feet.

The Mask’s eyes widen, and he lunges. “Witch!”

I throw myself out of his path, hurling the torch at the nearest pool of oil. It flares with a roar, distracting the Mask, and I use the moment to tear away from him.

Disappear, I tell myself. Disappear! But I’m going too fast—it’s not working.

But it must work, or I’m dead. Now, I scream in my mind. The familiar ripple runs back over me just as a tall, thin figure steps out of a hallway and swivels his triangular head toward me.

Though I wasn’t sure I’d recognize him based on Helene’s description, I know him immediately. The Warden.

The Warden blinks, and I cannot tell if he saw me wink out of sight or not. I don’t wait to find out. I hurl another can of blue-fire oil at his feet, rip two torches off the wall, and throw one down. When he shouts and jumps back, I swerve around him and hurtle down the stairs two by two, dropping the last can of oil as I do and pitching the final torch over my shoulder. I hear the whoosh of flame as the stair railing catches fire.

I have no time to look back. Soldiers rush through the rotunda, and smoke pours from the hallway near the kitchens. Yes, Bee! I pivot around to the back of the staircase, the spot where Elias said he would meet me.

A heavy thud sounds on the staircase. The Warden has leaped over the fire and stands in the rotunda. He grabs a nearby aux by the collar and snarls at him: “Have the drum tower deliver the evacuation message. Auxes are to herd the prisoners in the yard and muster a cordon of spearmen to prevent escape. Double the perimeter guard. The rest of you”—his crisp roar brings every soldier in earshot to attention—“proceed with the evacuation in an orderly fashion. The prison is under attack from within. Our enemy seeks to sow chaos. Do not let them succeed.”

The Warden turns to the interrogation cells, pulling open the door just as three Masks spill out.

“Bleeding inferno down there, Warden,” one of them says.

“And the prisoners?”

“Only the two, both still in their cells.”

“My medical equipment?”

“We believe Drusius got it out, sir,” another of the Masks says. “I’m certain one of the Scholar brats set the fire, acting in league with Veturius.”

“Those children are subhuman,” the Warden says. “I doubt they are capable of speech, much less a plot to burn down the prison. Go—ensure the cooperation of the remaining prisoners. I will not allow my domain to descend into insanity over a bit of flame.”

“What about the prisoners down there, sir?” The first Mask nods to the stairs leading to the interrogation block.

The Warden shakes his head as smoke billows from the doorway. “If they’re not dead already,” he says, “they will be in seconds. And we need every man in the yard, controlling the prisoners. Lock that door,” he says. “Let them burn.”

With that, the man clears a path through the stream of black-clad soldiers, delivering orders in his high, crisp voice as he goes. The Mask he spoke to slams the interrogation door shut, throws a bolt, and secures it with a padlock. I sneak up behind him—I need his keys. But when I reach for the ring, he senses my tampering and swings his elbow back, connecting with my stomach. As I double over, gasping for air and fighting to maintain my invisibility, he peers over his shoulder but is pulled away by the rush of soldiers pouring out of the prison.

Right. Brute force. I yank one of Elias’s scims from my back and hack at the padlock, not caring about the racket. It’s hardly noticeable above the roar of the approaching fire. Sparks fly, but the lock holds. Again and again I swing Elias’s blade, screaming in impatience. My invisibility flickers in and out, but I don’t care. I must get this lock open. My brother and Elias are down there, burning.

We made it this far. We survived Blackcliff and the attacks in Serra, the Commandant, the journey here. It cannot end like this. I will not be done in by a bleeding, burning lock.

“Come on!” I scream. The lock cracks, and I put all of my rage into the next blow. Sparks explode, and it finally opens. I sheathe the sword, and fling the door wide.