Who sent me a letter?

Tomorrow Sophie will turn 40 years old.
However, she still behaves like a girl: going to bed alone, leaves the light in the bathroom and lies so as to see the door open. On the eve of his anniversary, Sophie suddenly wakes up in complete darkness and with horror discovers directly opposite the bed of a stranger.
He takes out a letter from his pocket and tells Sophie to open it in the presence of all his relatives and friends at the celebration of his birthday, exactly eight Evenings. Otherwise, her mothers and sisters are in mortal danger!
The man disappears as suddenly as he appeared, and Sophie covers a real panic. Maybe this is some kind of mistake? But in a letter with a faceless seal of red wax, her name was printed, and the stranger clearly did not joke about the threat. And that means she will have to fulfill his condition