The TARDIS sang of joy and sorrow in that ever-present hum that only her bonded soul could hear.
He wasn't listening.
He stalked her halls, deep and vast, his countenance dark and his hearts wounded. She laid down new passages as he trod, empty rooms, dizzying staircases and exponential mazes. She made certain he did not stumble onto any memories, tucked away Donna's room (with its mountain of forgotten luggage) where he would not find it. Not now, perhaps not ever.
Time was meaningless in the vortex, especially so since there were no humans to keep the Time Lord and the Time Ship company. And since there was no Gallifrey, absolute time could no longer be calculated. There was only ebb and flow, the natural cycles of his physical body that even Time Lords could not ignore indefinitely: hunger, thirst and exhaustion.
The TARDIS bided her time, as she had so often before. He would eventually tire and sprawl on the floor in a dim corridor or secret garden. And as he gazed up at gray walls or soaring arches, he would sleep.
And there it was -- days of walking finally saw him stumble into a wine cellar. He stubbed his toe on a casket and fell onto the cold stone floor. He was too exhausted to curse and merely sighed and surrendered to his body's needs.
Whereas his waking mind churned with inconsolable guilt and razor-sharp sorrow, she could soothe his dreams.
She sang of death and birth and renewal, of terror and faith and love. She exulted in a console room full of pilots, and shared with him her affection for each of them. For her consciousness is not the purview of her Doctor alone -- every soul who travels with her touches her as they do him. They leave indelible imprints on her and help shape her in times to come. Ancient she may be, but she is ever-changing, too.
He dreamt of fire and violence, but she tempered his rage with echoes of loved ones. Rose's compassion, Sarah's insight, Jack's solid presence and Martha's healing all wove through his dreams. And finally, when he had quieted and she knew he would listen, the TARDIS reminded him of Donna's courage. That spark in her that dwelt just beneath the surface, that could burst to life when adversity or challenge blocked her path. The spark that nothing could extinguish.
Satisfied that he got the point, the TARDIS released him and he fell into a deep, dreamless sleep that stretched beyond reckoning.
He awoke at last chilled and sore and grumbling, which was a relief. He was not whole again, no one so defined by loss could ever be. But his fractured pieces cleaved together and a new shape was forming. The Doctor was nothing if not resilient.
Eventually, he stirred enough to sit in his navigation dome and gaze at the stars that Donna had saved. From here, he could call up any sky view, from any coordinates in the universe, as it existed at any time in creation. Not merely the two-dimensional pinpricks of light of an earthly planetarium, but vibrant stars in multi-dimensional form. He walked into the starfield, pondered the constellations and nudged his brain into calculating their retro-densities and xenthian inertia.
The TARDIS hummed her approval.
The math flowed, calculations tumbled into one another. He challenged himself and increased their complexity. Soon he was skimming across the stars and working with quasars and pulsars, black holes and fractional strings. A current of dark matter caught his eye, and out came the glasses.
He traced it backwards to a black hole in the Mirith galaxy and forwards to another in the Paladium Cluster. Like a massive trade wind, it flowed around stars and gravity wells spawning maelstroms and churning nebulae like a cosmic lava lamp.
And he smiled. One day, he'd park the TARDIS along the current and drift wherever it took him.
He pocketed his glasses and sniffed, encouraged his sense of smell to awaken as his mathematical skills had. He sensed ozone, dust and the metallic tang of an impatient TARDIS. The stars that danced around him all at once seemed dull and lifeless. It occurred to him that replicas weren't enough to do justice to Donna's achievement.
Living stars, that was the ticket, and he knew just the place.
The console room thrilled at his return, lights glowed artfully in yellow and green, anticipating the purpose that only her pilot could provide.
The gas giant Yar-tasana loomed large in the sky as the Doctor set down on its furthest moon. The atmosphere was thin and the gravity ponderous, but serviceable for a Gallifreyan. The view, however, was worth it. The moon's orbit spun so rapidly that it made its circuit in a matter of six hours. It was in essence a revolving platform that gave an unparalleled view of the entirety of the Milky Way. The Doctor found a hillock created by meteor ejecta and laid down a blanket (the moon's soil clung to fabric and there was no sense in ruining yet another suit). Hands linked behind his head, he laid down and stared up at the stars.
They were alive. He reveled in that thought for some time as he identified them like old friends. Time churned along and Sol came into view. That most mediocre of stars that gave life to Earth, his adopted home.
They were alive because of Donna. Not just here, in the rather pedestrian spiral arms of the Milky Way, but the other galaxies, too. And e-space and n-space, divergent parallel realities and everything in between -- all the grandeur and the chaos, the entropy and the dizzying variety of life.
He laughed, a sharp bark of joy. "Thank you Donna Noble," he said. Then smiled through his tears.