Zhou Yan had practiced his family's inherited spirit-summoning ritual for years. At last, he summoned someone.
His own self from yesterday.
It was a shifting mass of colored light with no discernible face. It never spoke, only repeating actions from the past. By touching it, he could briefly witness the past from his own point of view, and make an action from long ago take effect again in the present.
Three seconds at a time, for seven days.
At first, he used it to find missing parts and check work orders he'd misremembered, until a deliveryman he knew vanished behind a door Zhou had just repaired.
The same old door led to the maintenance room that morning. But when he approached it from a different direction and opened it again, there was another corridor beyond. The missing man's cries for help came from deep inside, while the mechanism that opened the door remained in the original room.
Zhou Yan began asking his past self for help.
After the missing man was brought back, a batch of equipment awaiting transfer came to light. Someone began keeping an eye on Zhou's work orders, his routes, and the exact spot where he reached out each time.
He saved people with actions left behind by his yesterday.
And the other side was arranging the kind of "yesterday" he would be able to borrow tomorrow.
