Underwood crossed to a cupboard at the back of the study, rummaged within it, and returned, carrying a metal cylinder. He shook it: from four small holes at its top, a white powder was emitted, which quickly spread out to fill the room. Whatever the powder did, the effect was immediate. Underwood gave a start and stared upward—directly at Nathaniel. It was as if the disc was a window and he was looking directly through it. For a moment, Nathaniel thought his master could actually see him, then he realized it was simply the suspended imp that hung revealed.
Horror—stricken, Nathaniel watched his master bend down to the carpet and pull at a loop of ribbon. A great square section of carpet peeled up and fell away to one side. Below were two painted pentacles. His master stepped inside the smaller, never for one moment taking his eyes away from the frozen imp. He began to speak, and within seconds a tall misty apparition appeared within the larger circle. Underwood uttered a command. The apparition bowed and vanished. To Nathaniel's amazement, Underwood's body seemed to shimmer and slide away from itself. His master still stood within the pentacle, but another version of his master, ghostlike and see—through, stood alongside it.
The ghostly form lifted into the air, kicked its heels and began to float forward—straight to where the helpless imp was still relaying the view from the study. Nathaniel screamed commands and shook the disc in fury, but could do nothing to stop his master's slow approach. Closer, closer… The spectral eyebrows were lowered, the glinting eyes never looked away. Now Underwood's form swelled to fill the disc—it seemed as if it would break right through…
Then nothing. The disc showed the study again, with Underwood's physical body still standing motionless in the pentacle.
Despite his panic, Nathaniel knew all too well what was happening. Having located the spy and safely frozen it in position, Underwood had decided to follow the imp's astral cord back to its source to learn the identity of the enemy magician. Such sources might be many miles away; perhaps his master was expecting a long journey in his djinni—controlled form. If so, he was about to get a surprise.
Too late, Nathaniel realized what he had to do. The window! If he could throw the disc out into the street, perhaps his master would not guess…
He had only taken two strides in the direction of the skylight when, without a sound, the translucent head of Arthur Underwood welled up through the floorboards. It was see—through and glowing with a greenish phosphorescence; the tip of the dilapidated beard extended into the floor. Slowly, slowly, the head revolved through ninety degrees, until at last it caught sight of Nathaniel standing above it, holding the scrying glass in his hands.
At this, an expression appeared on his master's face that Nathaniel had never seen before. It was not the familiar look of impatient disdain that had long characterized Underwood's tutelage. It was not even the fury he had witnessed that morning, following the discovery in his room. Instead, it was first a look of extreme shock, and then a sudden explosion of such malice that Nathaniel's knees gave way. The disc fell from his hands; he slumped against the wall; he tried to speak, but could not.
The ghostly head stared at him from the center of the floor. Nathaniel stared back; unable to tear his eyes away. Then—very muffled and distant, perhaps because it was uttered by the physical body in the study far below—Underwood's voice came sounding from inside the upturned disc.
"Traitor…"
Nathaniel's mouth opened, but let forth only a strangled croak.
The voice spoke again. "Traitor! You have betrayed me. I shall discover who is guiding you to spy on me."
"No one—there's no one…" Nathaniel could only manage the barest whisper.
"Prepare yourself! I shall come for you."
The voice faded. Underwood's head descended, spiraling into the floor. The phosphorescent glow vanished with it from the room. With trembling fingers, Nathaniel picked up the disc and peered into it. After a few seconds the view of the study grew misty as his master's spirit form passed back through the imp; it drifted away across the carpet to where the body waited. Coming alongside, it adopted the exact same posture and merged in with itself. A moment later, Underwood was himself again and the shadowy apparition had reappeared in the other circle. With a clap of the hands, Underwood dismissed the djinni; it bowed and vanished. He stepped out of the pentacle, eyes blazing, and strode out of shot toward his study door.
At this, the spell on the imp was lifted and the baby's face returned to fill the disc. It blew out its cheeks with relief.
"Whoof! I don't mind telling you, that was bad for my system," it said. "Having that horrible old geezer drifting straight through me and right up my cord… it gives me the willies just to think about it, it really does!"
"Shut up! Shut up!" Beside himself with terror, Nathaniel was trying to think.
"Look, do us a favor," the imp said. "You haven't got much time left. Couldn't you just free me now, before you die? Life gets so dreary in this disc; you don't know how lonely it gets. Go on, boss. I'd really appreciate it." The baby's attempt at a winning smile was interrupted as the disc was hurled against the wall. "Ow! Well, I hope you enjoy what's coming to you, then!"
Nathaniel ran to the attic door and rattled desperately at the handle. Somewhere below he heard his master's footsteps hastening up the stairs.
"He's really angry," the imp called. "Even his astral form practically pickled my essence as it went by. I wish I wasn't facing the floor—I'd love to watch what happens when he gets in here."
Nathaniel sprang at the wardrobe, pushed at it frantically; he planned to push it in front of the door, to block the way in. Too heavy, he hadn't the strength. His breathing came in fits and gasps.
"What's the matter?" the imp asked. "You're a big magician now. Call something up to save your skin. An afrit maybe—that should do the job. Or what about that Bartimaeus you're so obsessed with? Where's he when you need him?"
With a sob, Nathaniel stumbled back into the center of the room and turned slowly to face the door.
"Nasty, ain't it?" The imp's voice dripped with satisfaction. "Being at someone else's mercy. Now you know what it feels like. Face it, kid—you're on your own. You've got no one there to help you."
Something tapped on the skylight window.
After an instant in which his heart nearly stopped, Nathaniel looked: a disheveled pigeon was sitting beyond the glass, gesticulating urgently with both wings. In doubt, Nathaniel stepped closer.
"Bartimaeus…?"
The pigeon rapped its beak several times against the pane. Nathaniel raised his hand to undo the catch—
A key rattled in a lock. With a bang, the bedroom door burst open. Underwood stood there, his face pink with exertion and framed by a furious white mane of hair and beard. Nathaniel's arm dropped to his side; he turned to his master. The pigeon had vanished from the window.
It took Underwood a moment to regain his breath. "Miserable boy! Who is controlling you? Which of my enemies?"
Nathaniel could feel his whole body trembling, but he forced himself to stand stock—still and look his master in the eyes.
"No one, sir. I—"
"Is it Duvall? Or Mortensen? Or Lovelace?"
Nathaniel's lip curled at the last name. "None of those, sir."
"Who taught you to make the glass? Who told you to spy on me?"