Disclaimer: I do not own Doctor Who (BBC does). I am making no profit from this story; I simply love to write.
Notes: Tenth Doctor, in the new series. The Master as shown at the end of Series 3. Spoilers up until then.
He is not the man you remember.
Hold him prisoner for a year. Stick him in a cage, a doghouse, a cell. Age him and make him look so very wrong—but he is not the man you remember. Not the child you grew up with, nor even the Time Lord you battled across the stars with. Something is completely different, something you can't define.
He is not, not at all, the man you remember.
There's something in the eyes. Something older. Colder. Darker. Greater. Still the Doctor—oh, he could never not be—but there is something in him you didn't want to define. Something that frightened poor old Professor Yana, something that even frightened the Master lurking inside the kind, old, human genius. Something different and something dangerous.
He frightens you now, and it's not just because he's floating in the air above you, turning your own psychic network against you, and ruining all your plans. He's always been brilliant (the smarter of the two of you, truth be told). That's no surprise. What is surprising is that you were always the ruthless one, and yet he's outdone you this time.
He waited a year. Waited an entire bloody year for his plan to mature, sitting quietly in the corner and making you think that he's hurting and shocked and lonely, just starved enough for the companionship of another Time Lord that he's not sure if he can end this or not. Except he was never not certain, was he? He's certainly in control now, towering over you like the worst nightmare you ever had.
Oh, this is a nightmare. Because he's not the boy you called friend, or even your best enemy any more. This isn't the Doctor you knew. Not the Doctor that your cold little black heart loved.
Loved to torment. Loved to battle with. Loved to face down.
This one is ruthless. Implacable. This one fought in the war you abandoned, fought and won and destroyed. This one made the choice that you know, in your heart, the others ran away from, too. This one did what was necessary, got carved up inside from it, and still somehow went on.
You couldn't do that. Neither could the Doctor you remember. Not the good man, the kind man, the one who believed in the best in everyone. He doesn't anymore. Oh, no. Not any more.
You didn't break that out of him. The war must have. He's the same but different, and you miscalculated because you didn't understand that, and yet all you can do for these few crucial seconds is curl up and grieve for the friend you once had—and wonder how it might have been different if you'd stayed to fight with him the one time it mattered.
Not against. With. Side by side. Then, he might have preserved the man you remembered, not the one who begged you with such an edge in his voice. "Look, we can leave. We can fight across the stars, if that's what you want. But not here, not Earth."
You didn't hear the edge in time. Didn't understand that the pain had finally become so great that it made him stronger.
During the war, you'd laughed when you heard that the Doctor terrified the Daleks. That they called him the Oncoming Storm. You'd spent a good fifteen minutes laughing about that one each and every time you heard it, because stupid-fool-you, you never thought to ask.
Even when you thought you'd caught him so easily, you never thought to ask. Never stopped to wonder if he had changed.
Because he's the Doctor. He doesn't change. Except he has.
And when you say "I win," what you mean is that you don't understand. That you don't think he wants to be responsible for you and that it scares you that he's willing to, because he isn't the man you remember, and nothing can ever be the same again.