The Doctor flipped two levers and a countdown appeared on the screen. "I just activated the TARDIS self-destruct system. One hour until this ship blows."

Bram ran to the door but it slammed shut.

"Don't try to leave," the Doctor began, "The TARDIS is in lockdown. I'll open those doors when Clara's by my side."

"You crazy lunatic!" Bram growled.

The Doctor spun around and floated stiffly toward Bram, his arms crossed and his chin jutting out. "My ship, my rules!"

The air felt different. It was trembling around him with potential energy. It felt as if he wasn't just using it; maybe he could actually control it if he wanted.

"You'll kill us all. And the girl," Gregor said.

"She's going to die if you don't help me. Don't get into a spaceship with a madman," the Doctor said.

Gregor ran to the doors and they both attempted to force it open.

"Didn't anyone ever teach you that?" the Doctor added, floating gently back to the console.

The feeling in the air was gone.

"Okay. A little gentle persuasion. Say 30 minutes," the Doctor said as he flipped some switches and pressed a button.

The countdown dropped to 30 minutes.

The Doctor suddenly felt something wrong. The TARDIS was scared.

The Doctor broke into a run. "Come on, Tricky!" he called as he jumped into the air and flew through the corridors.

Tricky ran after him, slowly falling behind. The Doctor swerved and flew into the Architectural Reconfiguration System room, where Gregor was about to cut one of the invaluable glowing crystals off its stem with a laser. The Doctor landed, but somehow the air continued and gently blew Gregor.

The Doctor didn't have time to question. "No! No, no. Stop! Please!"

Gregor lowered the laser as Tricky ran in.

"Don't! Don't touch it. Please," the Doctor continued as he slowly approached Gregor. "She won't let you touch it. I can feel a TARDIS tantrum coming on." He lovingly stroked one of the teardrop crystals.

The Doctor walked into the console room, followed by Tricky.

"Back where we started," Tricky said, recognizing the room.

"No. It's an echo," the Doctor said as he flew up the steps to the console, "The console room is the safest place on the ship. It can replicate itself any number of times. It's trying to protect us," he continued as he flew around the console.

"Because I tried to give back the circuit?" Tricky guessed.

The Doctor patted Tricky's face as he flew by. "Team TARDIS."

The Doctor accidentally knocked a piece off the surprisingly fragile console as he worked the controls. The piece suddenly vanished.

"Where did . . . where did that go?" Tricky asked.

"There's more than one echo room." The Doctor noticed a shadow moving out of the corner of his eye and pointed at it as his feet touched the ground. "Hey, look, look! The TARDIS has got Clara safe. That was her. That was her there." He kissed his fingers and his feet rose off the ground as he pressed his fingers against the engine column. "Thank you! Thank you! Thank you!"

"Why can't we see her?" Tricky asked as the Doctor let his feet touch the ground.

"It's like a light switch. Two positions. Flickering at super-infinite speeds. We're only together for a brief second." The Doctor thought he detected movement. "Shh!" He floated slowly and silently around the console.

Clara's frightened breathing echoed in the room, muffled.

"I can hear her," the Doctor said quietly. He floated gently, listening for Clara's breathing. He heard a distant scream. "She's let it in. She's let it in!" He frantically worked the controls. "Ah . . . if I can just isolate her position, I can nudge the alternation, reach in and grab her."

"Console room, echo imprint of the original," Gregor's handheld computer said.

The Doctor and Tricky spun around to see Gregor with his computer.

"You're coming with me. I need you to get me out of here," Gregor said.

The Doctor buzzed the sonic screwdriver at the computer.

"Scanning for female human," the computer said.

Gregor followed the signal around the room.

"Scanning for female human."

Gregor continued walking.

"Unidentified human," the computer said.

The Doctor flew and took the computer from Gregor. "It doesn't know Lancashire."

"What?" Tricky asked.

"It doesn't know sass," the Doctor continued, "Yes! It's found Clara! It's found her. She is right there." The Doctor buzzed the sonic screwdriver in Clara's direction and a faded image of Clara flickered into view, cringing against the wall where the door would be.

The image screamed at something. The Doctor flew toward Clara, grabbed her, and pulled her into the room, still screaming. She pulled away and spun around, breathing hard in fear and confusion.

"It's all right. Clara, I'm so, so sorry," the Doctor said, "Please, please forgive me . . . ."

Clara punched him in the shoulder and walked away.

"Ow!" the Doctor said, rubbing his shoulder, "Okay, so we're not doing hugging, I get that now."

"What do you keep in here?!" Clara shouted, upset, "Why have you got zombie creatures? Good guys do not have zombie creatures. Rule one." She punched him again.

He floated in the air defensively, high enough that she couldn't hit his shoulder again, even though he knew she could hit him somewhere else.

"Basic storytelling," Clara finished, still upset.

"Not in front of the guests," the Doctor said in frustration.

Clara noticed Tricky and gave him a little wave. "Who are they?"

"Friends. Well, people who aren't trying to kill us, so I don't need punching again!"

Clara glared at him before walking away and leaning against a rail. With Clara relaxing, the Doctor felt safe to come back to the ground.

Gregor grabbed Tricky and pulled him back onto the catwalk suspended above the power source. The Doctor watched in horror as their skin burnt and melded, forming them into the deformed double zombie Tricky had just thrown over the side. While it was temporarily distracted, the Doctor grabbed Clara's hand and flew, pulling her past the creature toward the door. He landed on the other side of the door and quickly closed and locked it with the sonic screwdriver.

The Doctor looked up at the door on the other side of the room. "The engine room. The heart of the TARDIS," he said. He took Clara's hand and they walked through the door. The ground immediately fell away as they stood on the edge of a bottomless cliff.

"We're outside," Clara said in surprise.

"No, we're still in the TARDIS," the Doctor corrected.

"There's no way across," Clara said.

"Not necessarily." The Doctor turned his back to Clara. "Hop on." He grunted when she jumped on his back. He faced the cliff and jumped. His feet came back to the ground on the edge of the cliff. "Whoa!" he shouted, waving his arms as he lost his balance.

Clara quickly jumped off his back and grabbed his arm. After a terrifying moment, staring down the endless drop, Clara pulled him back up with a grunt. She leaned on her knees with a sigh as the Doctor stumbled away from the edge.

"That was not good!" the Doctor said, "That was very not good," he added, hopping madly in an attempt to fly.

"What's happening?" Clara asked.

"I can't fly!" the Doctor growled, flailing his arms.

The air wasn't helping anymore. He couldn't use it anymore. He was just a regular person using air for breathing only.

"Okay . . . ." Clara said slowly, "Just relax. I'm sure you still can."

The Doctor relaxed and thought for a moment. "No. It's gone. The TARDIS is blocking it. She got in my head and took it out."

He'd been able to fly for hundreds of years. He felt as if a part of him was missing. He felt helpless and powerless. It was even worse than the time he settled on a cloud in Victorian London and refused to get involved. At least then he could concentrate and fly a little. He couldn't fly at all. He couldn't even stand on the air. He couldn't even feel it.

"So what do we do?" Clara asked, pulling the Doctor out of his doldrums, "Time for a plan. Do you have a plan?"

The Doctor tried to perk up for her. "Well, no. No plan, sorry."

The Doctor floated high above the console, polishing the engine column, spending some quality time with the TARDIS after their harrowing adventure.

Clara walked in and leaned against the console with wet hair and a towel over her shoulder, having no memory of what had just happened. "I feel exhausted," she said, "I feel . . . ."

"We've had two days crammed into the space of one?" the Doctor asked.

"Why would you say that?" Clara questioned.

The Doctor vigorously rubbed a non-existent spot. "I don't know. I say stuff. Ignore me." He stopped rubbing. "Do you feel safe?" he asked, still staring at the column.

"Of course."

The Doctor faced her and floated down as he spoke. "Give me a number out of ten. Ten being whoo-hoo, one being . . ." he paused as he landed, "aarrrggh!"

Clara gave him a look. "You're being weird."