Nine hundred years of solitude.
Nine hundred years within the TARDIS, spinning through space and time, running to the edge of the universe simply because he had nobody to hold him back. Maybe a companion or two for a couple years, but in the end, it was just the Doctor and his TARDIS and the emptiness of space.
The pistol shakes in his grip. No running from inevitable death now; no running from this final conflict between the Master and the Gallifreyan President. He is the deciding factor, the one calling the shots, the one with no choice but to murder one or the other lest the planet of Gallifrey leap free from the timelock and smash Earth out of orbit.
The Master or the President. His archenemy or the man who seeks to end time itself.
He's spent the last nine hundred years running, and though he can face the death warned by those four sinister beats implanted in the Master by the President, he can't bring himself to execute either enemy.
Time freezes to a standstill. Not one person in the room moves—not the President nor his elite guards, not the Master behind him, not even Wilfred locked within his glass cage. Complete silence blankets them all as the Doctor stands in the center of the revived remnants of his race, unable to pull the trigger of Wilf's gun and sever the link pulling his home planet and his people and the Time War and all its horrors out of the timelock.
The pistol trembles as he stares down the barrel at the formation of five Time Lords—the President flanked by two guards and two women covering their eyes in shame: like Weeping Angels, those lonely assassins. In all of his nine hundred years of running, when standing in the middle of the room surrounded the people of his past—the people whom he's killed over and over again by locking them into a single moment of time, unable to travel outside of the unending Time War... the Doctor has never felt more alone.
And then, almost imperceptibly, the environment changes. An infinitesimal shift. A small psychic signature, calling his name gently. It's a soothing whisper, a familiar, haunting melody that curls around his mind and brings back warm memories of long, long ago out of the troubled, dark haze of his mind.
He recognizes her before she lowers her hands from her eyes. Her physical appearance, so aged and ancient, is nothing like memories of the youthful woman of his childhood… but he could never forget her psychic signature. He never would forget her. And in the moment that they make eye contact, the Doctor cannot hold that lonely, lonely child within him from springing forward desperately.
Mother.
He knows that she's heard him when a single tear slips down her cheek.
Her eyes shift off him. Her presence in his mind slips away, drawing all its comforting warmth, its pleasant memories of golden orange skies reflecting off silver-leaved trees and glowing mountains, its recollections of home, home, home, that one space and time in which his mother loved him—she looks away and it is gone and it will never, ever return, because she's telling him to sever the link and condemn Gallifrey to everlasting death within the Time Lock.
He's killing her. Over and over again, he kills his mother, he murders his family, he sends the President and the Gallifreyan government back into temporal imprisonment by whirling around and shooting the tiny white-point star.
By the time he looks back, ready to face death by the hands of President Rassilon, she's covered her eyes again. A flash of white, a roaring wind, a blast of furious electricity from the Master, and she is gone.
Mother.
And, as the last of the Time Lords yet again, the Doctor is alone.
A/N: I played "The Doctor's Theme" on loop while writing this—the song that plays when the Doctor first spots his mother and, according to composer Murray Gold, is associated with The Doctor's dark and private history: haunting, wordless vocals backed by an echoing string orchestra for the Tenth Doctor.