Jack tore down the corridor following the vibrations of the floor under his feet...something was moving, something big.

He skidded round a corner just in time to see a large glass panel slowly lowering into place. But it wasn't the glass that took his attention it was the sight of a huge sphere detaching itself from the rest of the ship.

Gut instinct told him he had to get on that thing and he took off again and dived, the panel scraping his back as he slid under it. Letting out a gasp of relief, he rolled over and found himself in what looked like an airlock, and the feeling of motion vibrated under his back.

He scrambled up and moved to what was most likely the only door in or out. There was only a small window, but it was enough for him to see the one thing he didn't want to see.

The Doctor and White Coat, standing only a few feet apart, only a small panel between them.

He could see the look on the Doctor's face and he didn't like it, not one bit. He hammered on the window, hoping that they would hear him, but neither man looked in his direction.

"Doctor!" he yelled and hammered on the window.

White Coat looked past the Doctor and stared at the large dark mass that was hanging above Earth. It dawned on him what his property was going to do.

"You're going to use this against that thing, it's not designed to destroy whatever that is!"

The Doctor gave him a half-smile. "Who said anything about using this thing to destroy it? There isn't a weapon powerful enough to destroy that, not anymore. This is a means to an end, a way in."

White Coat paled slightly. "You can't fly this thing into that, it eats planets for god's sake, and I for one am not ready to die," he said and pulled out a gun.

The Doctor's expression never changed. "It really wouldn't be a good idea to fire that would it. I know what this thing is made of. I know all the defence mechanisms. One shot and it'll have your hand off with the lasers. So put that away and accept whatever fate awaits you."

White Coat blinked and realised it had been an act of complete hubris on his part. He really shouldn't have believed he could control such a powerful alien. Now, it looked like he was going to pay the price, but he wasn't done yet.

"Do you really think you know all the workings of this weapon? You may have found the key to getting in, but you don't know what the key is to controlling it. This weapon won't activate without the right key."

The Doctor smiled once again. "Oh, I think I have a pretty good idea. You seemed pretty keen to get me back, well the insane me. I think the key is me."

The Doctor held up his hand and nestled in his palm was what looked like the skeleton of a cycling helmet with needles and wire attached to it.

"I think this the control and if I plug myself into it, I can control this weapon, what do you think?"

White Coat said nothing, but was staring past the Doctor. "I think we're dead."

The Doctor turned...the Chaos it was moving towards the sphere.

Jack couldn't hear the conversation, but he could guess. Anger had risen along with panic when White Coat had produced the gun, then consternation when he saw the Doctor hold up some sort of device.

Then he'd seen what White Coat had seen and he couldn't believe his eyes.

The black mass was huge and it was moving towards them and it seemed to be twisting and moving with a life of its own.

"Doctor, let me in!" he screamed, hammering his hand against the glass, but both men were focused of the dark mass that was approaching.

"I've never seen a thing like that," White Coat said, his scientific mind for once overtaking his thoughts.

"I have and you really don't want it here," the Doctor said. "It's called The Chaos, well my people called it that. It comes from a time we called the Dark Times. It's dangerous and mostly unstoppable."

"Mostly unstoppable?" White Coat said.

"My people found a way, but it obviously didn't destroy...he obviously wasn't strong enough," the Doctor said, a sad tone to his voice. "Guess it'll have to be me after all."

With that he placed the device on his head and for a few seconds nothing happened.

White Coat stepped back, he knew what was about to happen and he didn't want to get accidently caught.

The Doctor felt the coolness of the metal on his brow and stood waiting for the thing to power into life. Nothing happened and he frowned and was about to remove it when something akin to fire blazed through his mind.

This weapon was powerful he thought, but then he felt something else...something much older...much more powerful and it was an all consuming darkness...the Chaos!

Jack could nothing as he watched the Doctor place the device on his head. He too watched as nothing happened at first and then began hammering on the glass again when he saw the Doctor go rigid.

Then sudden realisation flashed through him, he had an energy pistol, the glass maybe bullet proof, but it may not be laser proof.

Standing back against what was now the outer lock he aimed the laser and fired.

The results were spectacular as the glass bent and shattered and the door exploded inwards.

Only White Coat reacted, pedalling backwards, away from the ruined door.

Jack rushed in and flew straight for White Coat, flooring and landing a solid punch to his jaw.

"Stay," he growled and turned his attention to the Doctor.

The Doctor had become completely rigid, as if he'd frozen in place, a look on his face that Jack could only describe as fear.

"Doctor!" he cried and ran over and reached for the device.

He got within an inch of touching when the floor moved under him and he was knocked off his feet. The sphere seemed to shudder and then it started to creak and groan.

Jack caught something in the corner of his eye and tearing his eyes away from the Doctor, he looked towards the large window at the front...and he took a physical step back.

The dark mass was engulfing the sphere...no it was actually penetrating the sphere, small black tendril appearing like wisps of smoke around the edges of the window.

Tearing his eyes away from the sight, he turned back to the Doctor...then his heart almost stopped.

Black tendrils were wrapping round the Doctor, curling around him like some smoky octopus.

"No," he whispered and stepped forward, but was stopped by what felt like an invisible hand. But it wasn't the hand that sent chills through him; it was the voice that came from the Doctor's lips.

"You will not touch the Chaos."