This is the third time this week. I wake up on the floor of the mill, surrounded by flour, my hands positioned against the gap between the stones as if I were measuring it in my sleep. The flour is white. It is fine. It is piled higher than it was when I went to bed. I did not make it. Or rather—I did make it, but I do not remember making it.

The mirror hangs on the far wall. It is an old thing, brought over from England by my grandfather, framed in wood that has darkened with age. When I look into it, I see a man I recognize and a man I do not. The first has my face. The second has my face and eyes that are not mine.

I am writing this in my journal because Dr. Whitmore told me to. He comes every Sunday, which is convenient because Sunday is my day off, and inconvenient because he uses my day off to tell me that my days are not real.

"The dissociative episodes are increasing," he wrote in his notes today. I saw him write it. I watch him write everything. He thinks I do not notice, but I notice. I notice everything. That is the problem, isn't it? Noticing everything and not knowing which of the noticeings belong to you.

"Julian," he said, closing the notebook. "How are you sleeping?"

"I don't sleep," I said. "Or I do, and when I do, someone else lives my life."

He made a note of that too. Someone else lives my life. He underlined it twice.

"The wheat," I said. "I need to tell you about the wheat."

He looked up. I had never volunteered information before. He always had to draw it out of me, and even then I gave him fragments—pieces of a mirror that I refused to let him see the whole of.

"What about the wheat?"

"I select each grain by hand. I turn it over in my fingers and I know. Some are good. Some are bad. The good ones go in the hopper. The bad ones go in the bin. I have been doing it for ten years. I know which is which."

"That is a skill, Julian. There is nothing wrong with a skill."

"It is not a skill."

"It is not?"

"It is something else. Something I cannot explain because when I try to explain it, the other one tries to explain it too, and his explanation is better than mine, and that is the worst part—not that I am losing my mind, but that my mind is being replaced by a better mind, and I cannot tell where I end and it begins."

Dr. Whitmore set down his pen. For the first time in a year of weekly visits, he looked uncertain. Physicians are not trained for uncertainty. They are trained for diagnosis, and diagnosis is the act of naming a thing so that it can be managed. But you cannot manage a thing that manages you.

"Show me," he said.

I showed him. I took him to the mill at midnight, which was illegal and dangerous and exactly what a patient should not do with his doctor, but Dr. Whitmore was a Whitmore and Whitmores do not follow rules. They make them. Or they try to.

The mill was dark except for the moonlight that came through the cracks in the walls. The stones were still. The wheat sat in the hopper, waiting. I stood between the stones and placed my thumb against the gap.

"Four millimeters," I said.

Dr. Whitmore measured. He used a caliper he kept in his coat pocket—a physician's tool, designed for measuring wounds, now measuring the distance between two grinding stones. Four millimeters. Exactly.

"Anyone can measure four millimeters," he said.

"Watch."

I closed my eyes. I placed my hand against the gap again. I did not look. I did not need to look. I felt the stones beneath my fingers and I knew—knew, not calculated, not estimated, knew—the exact distance between them, the exact pressure required, the exact amount of force needed to turn the upper stone at the speed that produced flour white enough to blind you in the dark.

I opened my eyes. Dr. Whitmore was staring at me.

"How?" he said.

I did not answer. Because I did not know. The knowing was there, sitting in my skull like a second brain, and when I reached for it, it was always there, waiting, patient, more patient than I had ever been in my life.

"You're frightened," Dr. Whitmore said. It was not a question.

"I am," I said. "But not of what you think."

"What do you think I think?"

"That I am crazy. That is what you think. You have been thinking it for a year. You have written it in your notes. You have told your colleagues. You have probably already submitted a paper. 'Case Study: Dissociative Identity in a Rural Mill Operator.' You will present it at a conference in Boston. They will applaud. You will accept their applause with the modest gesture of a man who has solved a puzzle."

Dr. Whitmore said nothing. His silence was an admission.

"But I am not crazy," I said. "Or if I am, the thing inside me is not crazy. It is precise. It is perfect. It adjusts the stones to four millimeters without looking. It sifts through eighty threads without counting them. It produces flour that is white and fine and better than anything any human being has a right to produce without paying for it."

"Who is producing it?"

"I don't know. It might be me. It might be him. I can't tell anymore. That's the thing you haven't understood, Edmund. You keep asking me who is in control. But the question is wrong. The question is not who is in control. The question is whether there ever was a who to begin with."

He left at two in the morning. He did not sleep. I did not offer him the couch. He drove home in his carriage with his notebook full of underlined phrases and his mind full of questions he would never publish because publication requires certainty, and certainty is the one thing a Whitmore cannot manufacture.

I stayed in the mill. I sat in the corner. I watched the mirror.

The mirror showed me myself. And behind myself, in the reflection, I saw another version of myself, sitting in the same corner, watching the same mirror, seeing the same reflection, and in that reflection, a third version of myself, watching, recording, smiling.

I am writing this now because I need to leave a record. If you are reading this, then either I am still here or I am not here and the other one is still writing, and you cannot tell the difference, and neither can I.

The journal is on the floor beside me. My hand is moving. I am not sure if I am moving it or if it is moving itself. The flour is white. The stones are turning. The gap is four millimeters.

I think.

Or someone thinks.