I've been trying to capture this moment since the first time I saw "The Waters of Mars," but it's taken me a while to feel I've gotten it quite right, to evoke the calamity lurking on the horizon. The final scene scared the pants off me, especially once the Cloister Bell rang.

Before the Fall
or
Tintinnabulation

She knew what she had to do. She had resigned herself to it before we even left the planet, and that's why I let my Time Lord take us to Earth. He needed to see this.

I suppose I could have just taken them someplace dangerous, some airless or toxic world where The Doctor's unique biology would allow him to survive while the Bowie Base One crew died instantly. No one would ever know that they weren't killed on Mars, and the timeline would be preserved. But then my Time Lord would have learned nothing.

Something had infected his mind, out there on the Red Planet. Loneliness, perhaps, or grief, or guilt. Or just helplessness. More likely a combination of all of them. Whatever it was, though, had been enough to finally break him. The last straw, as the humans like to say. He was going mad, and I had to snap him out of it somehow.

This was going to hurt. I'm sorry, my Doctor, I'm so sorry, I thought as I materialized–for once, exactly where and when he wanted me to.

When I heard him speak to Captain Brooke, I knew I had made the right decision. The Time Lord Victorious? Little people? I had never heard The Doctor speak that way before. I had never even heard him think that way before. Something in him had just snapped, and if he couldn't pull himself together, he would pull the Universe apart, moment by pivotal moment. Destroyer of Worlds, Davros had called him. He had no idea.

So I did what I could. I could only hope that by letting him see this through, by showing him the consequences of this most colossal mistake he'd ever made, I could save him from himself.

It was for his own sake as well as that of the Universe as a whole. The Doctor was a good man at heart, and left to his own devices, would eventually realize just what he'd done. But he could be single-minded, even obsessive, in his pursuits, and by then it might be too late. And then he really would go mad. I couldn't bear the thought of it.

And so I watched, a sick feeling churning in my core, as Adelaide drew her gun on her way into the house. My Time Lord had already turned to face me, smugly satisfied. I fervently wished I had hands—I wanted nothing more to shake him until that expression was wiped from his face. That was not my Doctor standing there.

I saw the flash of bluish light in the window, heard the unmistakable sound of an energy discharge. My Time Lord spun around, and I could read the horror on his face and in his gestures. His mind reeled. His daring rescue had been for naught, his bold revision of the Laws of Time undone. By a mere human being. And the magnitude of the crime he had committed came crashing down upon him. I could see him buckle under the weight of it.

And then, the summons.

I watched my Time Lord fall to his knees in despair. I heard him cry out, his voice bleak and broken. It hurt to see—he was always so strong, so brave. But now he had been brought face to face with the one thing in all the Universe that could make even his courageous hearts quail with terror.

Himself.

There had always been a darkness in him, and that darkness had exploded at the end of the Time War. Now it was poised to consume him, and for a moment, he cowered before it.

I waited, trusting in him as I always did. Trusting that he'd find the glimmer of light that still remained. But the darkness clouded his mind, and I couldn't read him.

But wait… yes, there was a glimpse of my old Doctor. The abject terror faded from his eyes, to be replaced by the cold, steely glint of determination. He stood, threw open my door, and strode into my control room, where our psychic link was strongest—

Oh. Oh, no. I could read him now, and still he was not my Doctor. He had seen what he had wrought, yes—and now he meant to run. The lines of convergence were being drawn, and he intended to leave this world to fall, the first in a long, long line. To flee his own destiny, his responsibility to the world he had sworn to defend.

I had one more way to try to get through to him, to find within my mad Doctor the Time Lord who was worthy of the title.

I tolled the Cloister Bell.

Catastrophe.