The Seven-Day Reset Rule

Lin Shen, the owner of an old bookstore, receives an anonymous package containing only three things:

A brass key engraved with "404",

An old street photograph taken sixty years ago but dated yesterday,

And a black notebook.

The first page of the notebook reads:

"Mr. Lin Shen, you will die in seven days."

The pages that follow contain a detailed countdown to his death.

Even more unsettling, this is the thirteenth such entry.