Eleven appearances. The Librarian has recorded each one. The intervals are not regular — forty-three days, then twelve, then one hundred and seven, then six. She has tested these numbers against every mathematical sequence in the archive and found no pattern.
She has also tested them against the movements of the sky and found something she will not record. She marks this entry with the small symbol she uses for observations that are true but should not be written down.
On the ninth appearance, a sound came from behind the door. The Librarian describes it as a hum — low, sustained, not mechanical. The hum lasted for the duration of the appearance and stopped when the door vanished.
On the tenth appearance, the hum was louder. Closer. As though whatever was humming had moved toward the door from the other side.
On the eleventh appearance — the most recent — the door was slightly ajar. The air that came through it was clean. Completely clean — stripped of dust, of moisture, of any trace that something had ever passed through it. The corridor smelled of stone and liquid memory. The air from behind the door smelled of nothing at all.
Entry 7,331, final annotation.
"The Guardian stood between me and the door. He looked at the space between us — the air, the silence, the gap where a decision had not yet been made.
The door closed on its own. The wall returned. The hum stopped.
I have filed this incident under 'Anomalies, Temporal' because I do not have a better category. But I do not think it is an anomaly. I think the door has always been there. I think the wall is the anomaly — a thing the corridor does to hide the door when it is not yet time.
Time for what, I do not know.
The Guardian does. I am fairly certain of this. He will not tell me. His usual silence is calm. This silence has weight.
I suspect there will be a twelfth."