The next floor

"What year is it?" The Superintendent asked as they left the lift on the next identical floor, where Audrey was talking with a dark-haired man and an Indian woman.

"2349, of course." Audrey replied, looking over at her.

"You didn't mention the president is coming here, when is she arriving?"

"The president of America is a woman?" Amy asked, following her friend.

"No, of course not." The Superintendent replied, "The president of the galaxy."

"You didn't ask." Audrey replied, "I think I might have solved your problem."

"You have?"

"My colleagues here are working on something that could have caused an interruption in the time streams." Audrey led them out of the main room and down a short corridor, to a heavy metal door which stood open. She gestured into the room beyond, where complicated circuitry covered one wall.

"Generating a singularity?" The Superintendent went in and looked at the circuitry. "A black hole, in a small room in a space station?"

"Not a black hole exactly," Audrey replied, staying in the doorway, "But something very much like one, they're working on protective shells for growing plants inside, and use this room to cleanse the environment of everything in it, like the ultimate clean room."

"Wiping out everything living, everything not living, sucking it all away." The Superintendent nodded.

"Super, is it safe to be here?" Amy asked, standing next to her.

"Oh, yes, it's completely deactivated." The Superintendent replied, "Just electronic parts right now, but hold on a moment..." she turned back to Audrey, "you're a plant nanobot scientist, how do you know about time streams? And how do you know what happened to my ship?"

"Ah." Audrey nodded. She thought for a moment, then slammed the door, with her on the outside.

"No!" Amy shouted, running back to the door but too late to stop it being sealed. Audrey looked at them through a small window.

"I knew you'd catch up with me eventually." She said through the thick glass, "I just hoped it would be after my nanobots had eaten the president."

"That sounds disgusting." Amy replied.

"Have we met before?" The Superintendet asked.

"Many times, but I might look a little different from the last few." Audrey replied. There was a cold glint in her eyes, and her mouth turned into a wicked smirk, "Your best enemy, the one you can never quite beat."

"You're a dalek?" Amy looked confused.

"I don't like you." Audrey sighed, then addressed The Superintendent again, "It's me, Supes... The Mistress."

She let out a short laugh, and pressed a control on her side of the door.

With a whirring noise, the circuitry on the wall lit up, and a pulsating black void began to grow in the middle of the room