Tegan heard the scream of her younger self and latched on to it, pulling herself towards it, flying out of the center of Torus like a cork.
She smashed her way into the cavern, crushing the Cyber-horde that stood in her way. She bent down and snatched the child up, cradling herself in the crook of her arm. She raised her other hand and forged it into the shape of a sword and in a single great sweep, thrust it deep into the glowing rock.
She felt the information flow up her arm from the lodestone and into her processors. She could almost feel the Doctor's mind delight in the numbers and permutations. When she withdrew her hand, the child was gone. She looked around the cavern, but there was only death and blood and silver creatures that hammered and gnawed at her outer plasmic shell. She shook them off and leapt back up into the sky, leaving the dead world of Karn behind her.
The data transmuted into a map within her mind. She could see all the lodestones scattered all throughout time and space, set there by Homeworlders so long ago, that held one fragile moment, a moment pure from cyberdeath and the Mara and the great sweeping nothing, held in place and taught by the lodestones, like a plastic tarpaulin, stretched tight and painfully thin. One plane in the crystal of time and space that was still the world she knew.
She could do this. They could do this. It was going to work.
The way to Torus was easier now. Space had shrunk and time had shriveled, devoured by the Mara and the nothing. Nothing stood in her way this time. And her excitement, she laughed at the thought, so close was she to home.
But the Mara was there by Torus, waiting for her, stupidly huge and very, very angry.
There was no sound in space, as it has already been said. But they were both part-TARDIS now and could speak without sound, without mouths, although they moved them anyway, out of habit.
"How many times do I have to kill you?" The Mara hissed, her head tilted, curious.
Tegan didn't have time for this. Something told her that the Mara knew that there was nothing else left, nothing left to eat, to kill, or to fear her. Which made Tegan feel strangely sad, in an odd, pitying kind of way. But she was in no mood for this. Instead, she grabbed the thick neck with improbable fingers and tried to hurl the monster out of the way. But the Mara was just as strong as she was, if not stronger, and could materialize and dematerialize anywhere, any when, just as easily as she could.
"And where are you going in such a hurry?" The Mara hissed.
Tegan realized that the Mara hadn't devoured Torus yet, had kept it to trap her and knew not its purpose. Yet.
Tegan felt a cold prickle against her skin, her hull skittering with block-transfer goose pimples.
The nothing was close. It was coming again.
This was it. Now or never.
It was too moronic to work but Tegan tried it anyway. She stared over the great serpentine head and said, "Look behind you."
Tegan wasn't sure if the Mara could sense the nothing too, or if she was just paranoid, couldn't help herself. She looked. And Tegan leapt.
Tegan felt a giant snapping as the jaws snapped at the empty space behind her, but it was too late. She was in the Nexus. And then Tegan made the TARDIS do what she needed it to do and she felt her skin grow and stretch.
The hull of the TARDIS could be as small as a gnat or large as a pyramid. Or as large as a moon. Or as large as anything that mathematics could model.
The TARDIS stretched itself across the entire universe, lodestone to lodestone, encompassing the single plane of time that the Homeworlders had preserved, as if it were dipped in amber. The time frame with no cyber race, with a dead adric, an imprisoned Mara and a terrified little Tegan who woke up from a strange dream in her bed at the age of eight. The TARDIS scooped it all up and vomited it all out through Torus into another, empty universe, one far removed from the Nothing and the Mara and the Cyber-horde.
But the TARDIS wasn't built to do that. It hung in the Nexus, in the heart of Torus, wounded and dying. But it wasn't going to be fast enough, Tegan knew that. The Mara had seen what Tegan had done, glimpsed the fresh and tasty new universe on the other side of the gateway, and she slithered towards the opening.
And Tegan did what she had to do. What the Doctor could not. Self-destruct.
The TARDIS exploded in a fiery blaze of light, obliterating Torus and the gateway. Sealing the way out.
Trapping the Mara in the dead and empty Universe. Alone.
In her rage, the Mara spat quaking gobs of saliva that jiggled and shook before collapsing against her hide, the gravitational pull of her body attracting everything around her, everything left in the universe.
And she sensed the nothing coming toward her.
She reared up and pounced.