Time phased into the TARDIS; the TARDIS phased into time; the TARDIS phased into itself; all of these were adequate but completely inaccurate descriptions of what happened when the TARDIS appeared back in reality, in nearly the same position it had been before, but slightly higher in the air. The knocking sound continued without missing a beat, except this time it was real.
The window looked out over the Clockworks again. The TARDIS whirled around it, mimicking the Master Room by never holding still long enough to be caught.
Amy was no longer frightened by it. The Doctor had taught her long ago that knowledge was the enemy of fear; the more you knew about something the more banal it seemed. She glared at the great machine as if it could see her—and who said it couldn't? "Okay. How do we stop it?"
"Stop it? We don't."
"But you said you could destroy it."
The TARDIS screamed. That was the only word for it. "Oh, no you don't," the Doctor muttered. He shifted it back out of time, then back in. "What? Yes, of course I could destroy it. But that wouldn't help us very much because—whoo—" Amy felt tingly. The Doctor cocked an eyebrow, almost smiling at the sensation. He pulled a lever the ship jolted in and out of the world again. "Sorry. Hold that thought, Amy." He stepped away, stopped, and turned around. "If anything happens, just toggle the wobbly lever."
He hopped across the floor and slid down the bannister, sonic screwdriver already in his hand. He was underneath the scaffolding now. It was all dangling wires and loose connections down there. He reached up and pulled down two mismatched cables. He stripped them with his teeth, and soldered them with the screwdriver. Green sparks exploded at the connection.
"What are you doing?" Amy called.
"Algebra!"
The tingling came back. It was a subtle inward pull that made the hair on Amy's arms stand on end. It didn't make her feel at all unwell, but it was not a welcome feeling either. Her hand shot out and she pulled a lever with a shiny black handle. The terrible knocking sound cut off, replaced by a rousing instrumental version of "God Save the Queen." But the pulling became even more intense. Like a massive hand was simultaneously crushing and stretching every part of her.
The Doctor yelled something from below.
"What?"
His voice was barely audible. He gestured urgently through the glass floor at a completely different part of the TARDIS. "The wobbly lever! The wobbly one!"
Amy's body felt too heavy and too light. Her head was like a balloon and her arms were lead weights. She used bits of the TARDIS control panel to drag herself toward the correct lever. With her last bit of energy she pulled it down. It was indeed wobbly. It had a loose screw or a broken belt. It came off in her hand. But the tingling-floating-crushing feeling disappeared. There was another shower of sparks from the room below. Amy caught her breath—
Amy caught her breath—
Amy caught her breath—
She was in a hall of mirrors. There was another Amy and another TARDIS control room inches away from her on either side. And beside them, others. She turned and looked behind her. Another Amy, another TARDIS. And another, and another. This wasn't double vision. It was infinite vision. She looked down at the lever in her hand.
The Doctor came up behind her. There were a million of him too, reflected against each other. He looked completely unruffled, and Amy hated him just a little teeny bit. "Oh, calm down. This was me, not you." His voice echoed and harmonized, sounding much bigger than it usually did. Followed at every step by multiple versions of himself, the Doctor took the lever from Amy's hand and tried to fit them back into the empty space. When that didn't work, he shrugged and left the lever on the control panel.
"Algebra," he said. "When you're working against something that divides time against itself, how do you win? Multiplication. Amy, meet yourself a few milliseconds from now. And a few milliseconds ago. How lovely is that. Bite me, Clockworks." He grinned. The control room was suddenly full of teeth. "Or rather, don't."
"Doctor," said Amy. She was very disoriented. The Doctor patted her hand.
"Stasis," said the Doctor. "We're simplifying the equation. What you felt a minute ago was the beginning of the TARDIS flying apart. We're safe now—for a while. Can you believe that it took almost the entire war to work this out? I did it with graph paper and a compass."
His voice had the tiniest echo. Also a bit of a buzz, which Amy thought was a—what—an echo that came before someone spoke. A pre-echo.
"Now, X equals what? That's our dilemma, Amy: What do Gorgorans and that—" The many Doctors pointed at the window. "Have in common?"
Amy looked out the window. Copies of the ice plains of Chvet were stacked on each other like an infinitely large deck of cards. But there was only one Clockworks, parked in the middle, churning and shaking. Smoke rose from its gears, which would roll forwards, then back, as if unsure of where to go. "They've both attacked us."
"Good. Right. And there's something else." He directed the TARDIS toward the Clockworks. "A lot of other things, in fact. Making me stay here. Making me fight an enemy I defeated a long time ago, an enemy that killed so many of my..." He seemed to lose the thread for a moment, but he grabbed back on with strength. "That's clever. That takes brains. And the Gorgorans forcing me into hom sleep: well, that was just vicious. I'm still not right."
Amy had trouble believing that anything could seriously hurt him. She didn't say anything though. Saying something wasn't the point. All that mattered right now was that she was there to listen.
"No," said the Doctor softly. "We'll slow it down for a while, but we're not going to destroy it. Not yet."
Infinite Doctors walked to infinite periscope viewers. The real image was just like the blueprint: same position, same parts. Except this Master Room was stuck, suspended in an equation of its own devising. He touched it. "The Gorgorans and this Clockworks share a puppet master. Pulling my strings. We can cut them, easily, but that's not a permanent solution." He spread his palm on the screen. At this distance, it completely covered the windowless, wooden room. "And you know how I feel about loose ends."
He focused on her. She was on the other side of the control panel, heart in her throat, afraid to move. "This isn't a fight anymore." There was a look in his eyes that Amy had never seen before, and she knew that she was seeing him as he had once been. Before he came home to Earth; before he had lost everything; long before he had met Amy and Rory and all the other people who saved from himself. Amy was frightened of him, and sorry for him.
"I'm going to get into that room, and I'm going to find out who's in charge." The multiplied Doctors didn't disappear, but Amy's world shrunk so that all she could see was her Doctor, right now, his voice absolutely cold and clear. "And whatever it costs me, I will repay with interest."
He beckoned. "Come and stand with me, Pond," he said. He pushed a few buttons, and the wooden room loomed large in the viewer. "We're going to war."