"Where are we?"

The Doctor asked as he picked himself off the floor, along with Zara. Zara had teleported them up, around where Ruri was.

"Above. You wanted me to bring you, so I have." She gestured around them, putting away her teleport device. "Now, follow me." Zara started walking forward, the Doctor following, looking round at everything. He pulled out the sonic and scanned the area, picking up different readings from down below.

"How do you know about up here? Rennarni told me if anyone knows about up here, they get taken." The Doctor asked, putting the sonic away, catching up to Zara.

"I'm hidden. Perception filter. Easy." She shrugged, turning a corner and heading down a corridor. "Not invisible, just not seen straight away."

"Then how come I could see you?" He narrowed his eyes.

"You're smarter than them."

"Yes. Who is 'them'?" Zara stopped outside a door, looking over at the Doctor.

"Do you mind?" She gestured to the locked door as he got the sonic back out and unlocked it. "And 'them' are just the foot soldiers."

"Foot soldiers?" The Doctor raised an eyebrow.

"Robots." She stepped through the door, the Doctor following. Zara suddenly pulled out a gun, causing the Doctor to step back, raising his hands.

"No guns!" He exclaimed. "That's not how I work." Zara raised an eyebrow.

"Yeah? Well it's how I work, Doctor." She walked past him, heading towards some equipment. There were different screens, showing different rooms. "Your friend-" She began, the Doctor rushing over, looking at the screens, spotting Ruri in one of the rooms.

"Ruri. There." He nodded, pointing to the right screen.

"Let's go get her." Zara strode out the room, the Doctor quickly following. They began to hear voices in the distance. Robotic voices. "Follow me. Keep low." She whispered to him. She held the gun up, quick stepping towards the door that Ruri was behind. "Doctor, use your device again, I'll keep look out." The Doctor complied, unlocking the door, opening it to reveal Ruri, who looked at her friend in shock and relief.

"Doctor!" She exclaimed, smiling as she ran towards him and hugged him. Before he had a chance to hug back, she had stepped back and slapped him.

"Ow!" He opened his mouth in shock, holding his cheek. "What was that for?!" He exclaimed, narrowing his eyes.

"What is rule one?!" She folded her arms. "Don't wander off! And what did you do?!"

"Me?!" He stared down at her in disbelief. "I didn't wander off! You did!" He pointed at her.

"No, you wandered off to talk to some aliens and left me where I got knocked over and when I got up, you -" She poked his chest. "Had disappeared."

"Oh." He swallowed.

"Yes. Oh." She narrowed her eyes, taking her gaze away from him as someone else entered the room. "It's you!" Ruri pointed at Zara. "You're the one who bumped into me."

"Yes. Sorry about that." Zara smirked, but it soon faded. "But we have to go. Now."

"Intruder alert." A monotone voice spoke from the door way, Zara turning and shooting the robot, disabling it.

"As I said. We need to go." She repeated, heading out the room.

"What are they?" Ruri asked, following with the Doctor.

"The foot soldiers." Zara told her. "Just robots. Robots always have a commander."

"Not always." The Doctor spoke up. "Some develop minds of their own."

"Yeah? Well, I haven't seen one yet." Zara said, leading them to the way out as alarms went off.

"Intruder alert." Voices exclaimed in the distance.

"So who are they the foot soldiers for?" Ruri asked, speeding up.

"No one knows. And I don't plan on finding out now." Zara said harshly, causing the Doctor to stop.

"The equipment. I recognise it." He stated, becoming frozen. "But it can't be..."

"Doctor... What is it?" Ruri stopped in front of him, seeing his worried expression.

"Oh Ruri... We never should have come here." He shook his head. "If it is what I think it is... We are all in danger." Ruri could see his concern, which made her concerned... And frightened.

"Ok, so what do we do? Stop them yeah?" She looked at him. He looked speechless and unsure of what to do next.

"We need to go!" Zara called from ahead, frustrated.

"Intruder alert."

"Doctor!"

"Intruder alert."

"Doctor? What's wrong?"

"Intruder alert."

"Let's go!"

"Exterminate."

Everyone froze, stunned by the new voice. It sounded... Robotic... Full of hate. Ruri felt fear rising, knowing the Doctor felt the same. Zara looked round them both, pulling her hood back over her head as she disappeared out, leaving the pair. Ruri looked at the Doctor, seeing his eyes full of anger and sadness... And fear.

"Doctor, what was that?" She asked quietly, her voice shaking slightly. He shook his head, looking down at her.

"The most dangerous being in the universe."